Backgammon is a game for two-handed board game. The narrow triangles are called "points", and the strip in the centre is the "bar".

Like Chess and Checkers, there is a standard symmetrical starting position.

Each player begins by rolling a die, and the player who rolls the higher number makes the first move. On each move a player's range of allowable moves is determined by the roll of two dice. On the first move the two dice used are the ones both players rolled, but thereafter the players roll their own two dice for their move. On the first move if the players roll the same number, they both keep re-rolling until the two numbers are different.

The rectangular board has quadrants called "inner boards" and "outer boards". Player A's two "boards" are the ones on his/ her side of the table. Each player begins with two checkers (or "men") in the opponent's inner board and five in his/her own inner board. Each player moves men in opposite directions, from the opponent's inner board through the two outer boards and then into their own inner board. Once a player has all fifteen men in their own inner board, he/she can then start removing men from the board, a process called "bearing off". The winner is the player who is first to bear off all his/her men.

A move in backgammon is to shift a checker or checkers from one point to another. If for example a player rolls a six on one the dice and a three on the other, the player can move one man six points and then another or the same man three points or can use the numbers in the other order. If a player rolls the same number on the same dice then the player uses it four times, to move up to four men.

A player is not allowed to move a man on to a point that has more than one of the opponent's men on it. To place a second man on a point is called "making the point". A single man on a point is called a "blot", and an opponent can move a man on to that point. Opposing men are not allowed to coexist on the same point. When the player lands a man on a point occupied by an opposing blot, he/she moves that opposing blot on to the "bar" (the strip down the centre between the inner and outer boards). To do this is to "hit" the blot.

A man on the bar comes off the bar by entering the opponent's inner board, landing on a point not made by the opponent. These home board points are said to number from one to six, the one point being where at the start of the game were two men. The player can enter on to the point designated by the dice. So if a player with a man on the bar rolls a four and a two, then the player can move the man on to the "four point" or the "two point" (in the opponent's inner board) if neither of these points are "made" by the opponent. It is possible to enter a man off the bar on to an opposing blot, hitting it. It is also possible that the points corresponding to the numbers rolled will (both) be made by the opponent, preventing the blot from coming off the bar. A player with a man on the bar is not allowed to move any of the men that are not there, so sometimes a player with one or more checkers on the bar will have no legal move and so miss a turn.

When a player has all his/her checkers in his/her inner board, that player can begin to "bear off". A player can use one or both dice numbers to take a man off the board. In this phase a player can use a six to take a man off the "six point" (where at the start of the game there were five men) or if there are no men on the six point then to take a man off the five point or there are also no men on the five point to take a man off the four point, and so on. In this bear-off phase a player can still move normally inside his/her inner board, and sometimes has no choice.

A five can be used to bear a man off the five point, or to move a man from the six point to the one point. If there are no men on the six point or five point then it can be used to bear a man off the four point, and so on. If a player has a man on the six point and no men on the five point, then with a five the player is forced to move a man from the six point to the one point.

Dice numbers can be used to directly bear off the corresponding point, or to move normally or if there isn't "room" to do that, then to bear a man off the highest point with a man on it. "Doubles" can be used to bear off up to four men.

It is possible for a player to be hit after he/she has started bearing off. In that case the hit player's bearing off is interrupted and cannot continue until all the player's not yet borne off men are again in the player's inner board.

Players must use as many of their rolled numbers as they legally can, but not necessarily to their "fullest extent".For example a player can use one number to move a checker in the bear-off phase and then the other number to bear it off as if that number was smaller. If a player can only play one or other number (but not both) then the player must use the larger number.

In backgammon a draw is not possible, but there are three degrees of winning. If at the end of the game the loser has borne off at least one man, then that is a "single game". If at the end of the game the loser has not borne off any men, and has no man either on the bar or in the winning player's home board, then that called a "gammon" and counts as a "double game". If at the end of the of the game the loser has borne off no men and also has a man on the bar or in the winner's home board, then that is called a "backgammon" and counts as a "triple game".

The Doubling Cube

Backgammon played for money or in a tournament usually uses the "doubling cube", which at the start of the game sits at the side of the board. On one face is the number "2", another the number "4", on others the numbers 8, 16, 32, and 64. At the start it usually has the number "64" showing, which is taken to represent the number "1".

Say a tournament match is being played. That is normally to some odd number of points, say eleven. That means that the first player to win eleven "points" wins the match. Here a normal single game counts as one point, a gammon counts as two points and a "backgammon" counts as three points.

At the start of the game the cube is said to be "in the middle" and is available to be used by either player. While it remains there, a player whose turn it is can before rolling "turn the cube" (from "1" to "2"). This is called "doubling" the opponent. The opponent then must decide to "accept the double" or not. If not, that game is over and the player who doubled has just won a point (as part of the race to win 11 points). If the double is accepted, then the game is then being played for two points and we say that "the cube is on 2".

The doubled player gets to have the cube on "his/her side", and now has exclusive access to it (is said to "own the cube") At some later point when its the doubled player's turn, he/she has the option to "redouble" (meaning that the cube is turned from "2" to "4"). Then the redoubled player can choose to either concede two points (ending that game) or to "take the cube" and play on for four points, and so on. "Single games", gammons and backgammons are scored as one, two or three times the "number on the cube" at the end of the game (1,2,4,8 or 16 etc.).

In tournament backgammon matches, when one of the players is for the first time one point away from victory (the target score), then in that one and only game the doubling cube is not allowed to be used. This is called the "Crawford Rule", and the one game it refers to is often referred to as "the Crawford game".

A different special rule normally applies in "money game" sessions, where the players have agreed to play for $x per point. That is called the "Jacoby Rule" and says that gammons and backgammons only count as single games unless the doubling cube has been used ("turned").

Another special rule can apply in money game sessions if the players agree beforehand as one of their ground rules, and that is "Beavers allowed". Normally if a player is not impressed with his/her opponent's double and would like to re-double, the doubled player must wait until after the opponent has rolled and moved, and then must surrender sole access to ("ownership" of) the cube. But if this special rule is in effect, then the doubled player has the extra option to accept the double and simultaneously redouble without giving up "ownership" of the cube.