The concept is simple. Eleven (or in some seasons, twelve) teams of two people who already know each other
are directed from location to location on the ultimate whirlwind tour. Along the way, there are tasks that
they must perform that will generally involve them in local culture, and test their adventurousness. In
Season 8, the Family Edition, they had ten teams of four people, which could include children.
The host is Phil "No Opportunity Wasted Is My Slogan" Keoghan, who had been doing television, mostly in New Zealand, for many years. His main line is travel/adventure shows, and that certainly fits here. He also makes for marvellous eye candy when standing in front of, say, the Taj Mahal or the Sphinx.
Ordinary checkpoints/clues are in yellow. The simple idea is to follow the instructions to get to the next checkpoint, or Route Marker in sequence. Route Markers cannot be skipped - skipped Markers must either be returned to out of sequence (if the place is nearby, like, in the same country), or players take a 24-hour penalty. Which one happens also depends on which season you're discussing. The rules of the game seem to be in a constant state of fine-tuning.
In Season 1, the clues were clues, meaning that you usually had to figure things out, rather than being told what to do, how to get there, and all with legalese and a glossary. The trouble was that teams got a little inventive with what the clue could mean, and the producers seemed to want to put a stop to it. This reduces the chances for clever gameplay (but doesn't remove it entirely), but makes for less whining about cheating.
A Detour is a choice between two tasks, each with its own pros and cons. Players must choose one of these tasks and complete it. It is possible to change your mind once you've discovered that your chosen task is difficult; you just return whatever equipment you might be using (a bicycle, a snowmobile, a set of eight barking, horny dogs, etc.) and go to the other task. This is a bad thing, because often the two tasks start in different places, and you waste time doing something that doesn't end up getting you anywhere. Often one task goes much faster than the other, though it may not be immediately apparent which one that is.
The Detour is sometimes immediately followed by a route marker type called the U-Turn, starting in Season 12. If a team (or two) gets U-Turned then that team has to do both parts of the Detour.
A RoadBlock is a task that only one team member can perform. The other player may not intercede except to yell out advice and encouragement from the sidelines. Unlike the Detour, once the decision has been made which way to go, the teams may not switch. The task is initially presented as a clue, such as "Who has a sweet tooth?" The team must then decide which member is more likely to do the task faster (or at all) and announce that that person is doing it. Then they can read the complete instructions of whatever it is they've gotten themselves into. There is usually one Detour and one RoadBlock on every leg of the race, even if they don't always make it to air. In Seasons 1, 10 and 12, there has been a RoadBlock on the first leg; this usually isn't the case. (The one from Season 1 wasn't aired—it was essentially the "really hungry" egg-eating task they reused in Season 5.)
In Season 6, they added the new rule that each team member can only do six of the RoadBlocks (or, from Season 10 on, no more than half, rounded up). In the first five seasons, teams could choose without restriction, which led to male-female teams putting up the male partner for almost all the challenges. In Season 8, with four per team, some RoadBlocks involved two people. In that season there were no restrictions on how many RoadBlocks an individual could do. In Season 24, this rule seems to have been waived.
A Face-Off is a direct competition between teams. It's appeared on the Canadian version of the show, and some international versions, but not the American one. The first two teams to arrive at the Face-Off compete at whatever task is there. The team that succeeds moves on and gets their next clue, and the losing team waits to compete again. This continues, releasing one team at a time. The team that loses the last time must remain at the site for a certain amount of time before they're released. A team will receive a longer penalty for bailing before another team shows up.
The Pit Stop signals the end of a leg of a race. This is the destination that the teams are ultimately trying to get to on a given day. At the Pit Stop, the teams check in and their finish time is recorded. Phil is usually there, along with a "local greeter" to congratulate the teams on their arrival. At times, usually on the first leg and the last half-dozen or so, the first team to arrive gets a prize consisting of a trip where they don't have to leave famous monuments mere minutes after arriving there.
On most legs, the last team to arrive at a Pit Stop is eliminated from the game. There are usually three or four non-elimination legs, and these tend to happen in the last half of the race. In Season 5 and 6, teams who arrive last have all their accumulated money taken from them, and don't receive money at the beginning of the next leg. We often see footage of people begging locals (or other teams) for cash. In Seasons 7 through 9, not only were teams stripped of all money, but all their possessions except for their passports and the clothes on their backs. This led to teams simply wearing all their clothes. This was sometimes amusing, but we ran out of all the possible permutations of how that could end.
In Season 10, we got a much better non-elimination penalty: that team gets "Marked for Elimination". If that team isn't first to hit the mat in the next leg, they get a 30-minute penalty, which may or may not finish them off. In Season 12, to increase the tension, they claimed that there were no non-elimination legs. This was a big, fat fib. Phil's little speech at the beginning of Season 12 belied this, and they introduced the Speed Bump (below) as a penalty to replace the end-of-leg waiting penalty.
A Fast Forward is a task that is optional. Teams can decide to go for the Fast Forward at any time during the race, but only after it has been revealed during a given leg. (Teams receive an extra clue in a green folder at some point.) They leave the course and go to a specified location to do an extra task. Completing the task means that they can go directly to the Pit Stop and skip all other tasks in between. The use of the mighty Fast Forward is controlled, however: Only the first team to complete the task may use it, and all teams can only use it once during the entirety of the race. Teams that have used up their Fast Forward during that leg are marked with a green background in the table at the end of each leg. In early seasons, teams that have yet to use a Fast Forward are marked with a double-triangle symbol.
In the first four seasons, there was a Fast Forward available in each leg; from Season 5 on, this has been reduced to just two, or just one in Season 8. In later seasons, teams that have used up their Fast Forward get the symbol. In Season 10, the one-team-one-FF rule got altered. A team that had previously used their Fast Forward couldn't prevent their co-Intersected team from using the Fast Forward, so in this case only, a team could use two Fast Forwards in a season. With Season 11, it seems that this suddenly-very-complicated rule has been dropped, and a team can go for every Fast Forward it finds. The one-team-one-FF rule was reinstated with the return of the Fast Forward in Season 20.
Seasons 18 and 19 didn't have a Fast Forward in them at all, so it's uncertain whether none was offered, or whether there were some, and since nobody went for it, they were simply never mentioned on-air.
An Express Pass is a special prize that was won in the first leg of Seasons 17 through 24 (or when there was $2,000,000 on the line, in Season 21, the second leg). It gives the team who won it the ability to skip any one task that they didn't want to do. It can be used at any time up to Leg 8. In Seasons 22 through 24, the team that won the Express Pass was given two Passes: one to use themselves, and one to give away to another team.
The Save is a special prize that was won in the first leg of Season 25. It gives the team who won it insurance against getting eliminated if they come last during a leg, but it can only be used once.
The Yield was introduced during Season 5. It gives teams the ability to slow down a team that's behind them. They remove the affected team's picture from a box and place it on a sign that's on the race course. They must also own up to Yielding the other team by putting their own picture at the bottom of the sign. When a team arrives at the Yield sign, they check whether their picture is there. If it is, they must turn over an hourglass and wait at the sign until the sand runs out. This seems to take minutes, though in theory, different timers could be used for different legs. If another team's picture is there, they can just bypass it. If no team's picture is there, they must either use the Yield, or announce that they choose not to Yield anyone. The Yield is similar to the Fast Forward in its oneness: only one team may use it in a given leg, one team may be Yielded, and teams can only use it once throughout the race. The ability to use the Yield has a physical component; one team, who lost the little picture they would use to own up to Yielding someone, said in an interview that this meant they simply weren't allowed to Yield anyone and no replacement picture was given. Teams that have used up their Yield are marked with a purple triangle symbol in the table at the end of each leg.
The U-Turn was introduced during Season 12. It also gives teams the ability to slow down a team that's behind them, but rather than using an hourglass, and having people untelegenically standing still, they have to go back and do whichever of the two tasks in the most recent Detour they didn't do the first time. The U-turn is structured exactly like the Yield was, pictures and all. As such, teams that have used up their U-Turn are marked with a purple triangle symbol in the table at the end of each leg. In Season 14, the "Blind" U-Turn was introduced, and the difference there was you no longer needed to 'fess up to having U-Turned your competition, and they're left to guess. Season 17 had a Double U-Turn, with two chances to U-Turn a team. A team that has been U-Turned can also U-Turn someone else behind them.
These two route marker types stir up emotional responses in Racers. Many teams who've been Yielded or U-Turned say that it's "unfair". Teams who nobly refuse to use it talk about avoiding bad karma and not playing dirty. All of this, of course, is preposterous. It can't be unfair or dirty play if the folks behind the Amazing Race itself give you the little picture in the first place and the rules say you have declare out loud whether you're Yielding anyone. If it's part of the game you've decided to play, then by definition, it's not unfair. On the other hand, many viewers—purists, the lot of us—dislike the Yield and U-Turn as a way of trying to create artificial drama on the Race when teams whine that they've been unfairly Yielded.
The Intersection was introduced during Season 10. It forces teams to pair up for all tasks until they are told it's every team for itself again. This includes Detours and Fast Forwards (which can now be awarded to two teams at once). Any decisions regarding what tasks to take must be made by the group as though they were a four-person team. A team can theoretically pair with any other team that has not paired up yet, but obviously it is in a team's best interest to pair with whoever shows up next, or whoever's there waiting for a team to show up. The Intersection was added along with the Yield as part of the Great Reform of Icky Rules in Season 10.
The Speed Bump was introduced during Season 12. It replaces the 30-minute penalty that meant you were Marked for Elimination. Instead, at one of the Route Markers on the next leg of the race, there will be a stand and clue box with the "marked" team's picture, directing them to a task that only they must perform. Once that task is completed, they must return to the Speed Bump location and continue on with the Race. Teams not affected by the Speed Bump can ignore it and just follow the regular Route Marker.
The Hazard was introduced during Season 19, though it appeared as a variant in Season 18. There's a task introduced before the teams hit the airport. The last team to complete the task will have a Speed Bump-y task of their own to do later in the first leg. In the Season 18 variant, the affected team were automatically U-Turned after the first Detour (which actually appeared in the second leg).