About the game

The backgammon game, in its actual form, is played on a board like this, with twenty-four triangles called points, in alternate colors. Backgammon is a game for two players, where each one has to move his checkers, according with the value of the two dice, into his own home board. The remaining twelve triangles represent the outer board, which is separated from the homes by the center area of the board called the bar.
Each player has fifteen checkers (stones or men) with a single color (here, black or white), placed in a start position as shown in the picture below. The points are counted starting in each one's home board, the outermost point being the twenty-fourth point (it is also the opponent's point one). You can also see in this picture a white arrow showing the direction of the White player movements. In the middle of the backgammon board there is a doubling cube, labeled with the figures 2, 4, 8, 16, 32, and 64 on its faces, used for keeping track of the current stake of the game.
 

The board for backgammon

You can see the checkers in their initial position, the player's homes, the doubling cube, the bar and the movement direction for the White player. The Black player moves in the opposite direction.
 

Objective

The objective of the game is for each player to bring all his checkers into his own home board and then bear them off. The first player to bear off all of his checkers wins the game. During the game, you can apply different strategy moves, such as to block the move or the entering of the opponent. You can also use the doubling cube to increase the stake of the game, if it is your turn and if this is allowed by the applying rules.
If you bear off all your 15 checkers before your opponent has borne off a single checker, you win a gammon, or double game. If you bear off all your 15 checkers before your opponent has borne off a single one, and he still has one or more checkers in your home board or on the bar, you win a backgammon, or a triple game.
A suite of games, played to a specified number of points, is called a match. This way the overall winner can be selected in competitions. The first player who reaches the required number of points wins the match. The points are awarded in the usual manner: one for a single game, two for a gammon, and three for a backgammon. More, the doubling cube is used such as the winner receives the value of the game multiplied by the final value of the doubling cube.
 

Rules

To start the game, each player throws a single die. This determines both the player to go first and the numbers to be played. If equal numbers come up, then both players roll out the dice again until they get different numbers. The player who got the higher number now moves his checkers according to the numbers showing on both dice. After the first roll, the players throw two dice and change turns.
The value of the dice indicates how many points, or pips, the player is to move his checkers. The checkers are always moved forward, to a lower-numbered point. A point occupied by a single checker of either color is called a blot. If an opposing checker lands on a blot, the blot is hit and placed on the bar. The following rules apply:
  A checker may be moved only to an open point, one that is not occupied by two or more opposing checkers.
  Any time a player has one or more checkers on the bar, his first obligation is to enter those checkers into the opposite home board. A checker is entered by moving it to an open point corresponding to one of the numbers on the rolled dice.
  The numbers on the two dice represent separate moves. For example, if a player rolls 4 and 1, he may move one checker four spaces to an open point and another checker one spaces to an open point, or he may move a single checker over a total of five spaces to an open point, but only if the intermediate point (either one or four spaces from the starting point) is also open.
  A player who rolls doubles plays the numbers shown on the dice twice. A roll of 6 and 6 means that the player has four sixes to use, and he may move any combination of checkers he feels appropriate to complete this requirement.
  A player must use both numbers of a roll if this is legally possible (or all four numbers of a double). When only one number can be played, the player must play that number. Or if either number can be played but not both, the player must play the bigger one. When neither number can be used, the player loses his turn. In the case of doubles, when all four numbers cannot be played, the player must play as many numbers as he can.
  When a player has brought all the checkers in its home board, he may begin bearing them off. If a die shows a number and in this point there is at least one checker, it can be borne off. If the biggest checker's point is lower than the number, the checker can be also borne off. If these conditions are not met, the player may try to move a checker to a lower point. Anyway, both dice have to be played if it is possible.
  The Jacoby rule is used in money games. It states that a gammon or backgammon may not be scored as such, unless the cube has been passed and accepted. The purpose is to speed up play by eliminating long not doubled games. The Jacoby rule is never used in match play.
  The Crawford rule tells that if you are playing an n-point match and your opponent is ahead of you and he gets to n-1 points you are not allowed to use the doubling cube in the next game to come. The Crawford rule is universally used in backgammon match play.
 

Glossary of backgammon terms

A
Anchor: A point where you have two or more checkers, placed in the opponent's home board.
Automatic Doubles: A rule which states that if the first roll of a game has the same numbers for both players, the stakes will be doubled.

B
Backgammon: The game we are talking about. Also the name of a backgammon game where a player borne off all the checkers, while the opponent still has a checker on a bar or in the winner's home. The player who wins receives three times the stake of the game.
Bar: The space in the center of a backgammon board, where the checkers are placed after they have been hit. If a player has checkers on the bar, he must enter them in the opponent's home before any other move.
Bear Off: Operation a player must do by removing the checkers from his home board, after all of them have been brought in there.
Black: A convention for naming the player with the darker checkers.
Block: A point with two or more checkers.
Blot: A single checker on a point, which can be hit.

C
Cube (doubling cube): Offered by a player to double the stake of the game. If the opponent accepts a double, he becomes the owner of the cube, and only he may offer the next double.
Checker (man, stone, piece): One of the fifteen (white or black) 'soldiers' of your 'army' moving around the board according to rolls of the dice.
Closed Board: A home board where all six points are blocked.
Contact: A board position where the players still attack each other.

D
Double: The offer made by a player to double the stake of the game.
Doubles (doublets): The name of two dice having the same value on their upper face, allows you to move four times the die's value.

E
Enter: Operation made with a checker from the bar which has to be placed in the opponent's home board according to the roll of the dice.
Equity: A number that globally reflects the chances of a player in a backgammon game position to win comparing the chances to lose. There is also a cube equity, showing the winning chances affected by the ownership of the cube.

F
Forced Play: The situation when the current dice roll can be played in only one legal way.

G
Gammon: A backgammon game where a player has borne off all the checkers and won the game, while the losing player has not borne off any of his checkers. The winner gets twice the value of the single game.

H
Hit: Move to a point where there is an opponent blot and put the checker on the bar.
Home Board: The opposite of the outer board, the place where players bear in their checkers.

I
Inner Table: the board side with the player's homes.

J
Jacoby Rule: A rule used in money games which says that the game counts as a single one if the cube has not been passed and accepted till the end of game.

K
Kibitzer: A person watching your backgammon game.

L
Lead: The pip count difference.

M
Match: A suite of games played until one player accumulates a certain number of points.
Move (movement): Process of moving your checker according to the value of a die, which may be entered, moved or borne off.

N
Nackgammon: A game variation, where a player has four checkers in opponent's home in start position.

O
Opening Roll: Each player throws one die to establish who starts the game.
Open Point: A board position occupied at most by an opponent's blot.
Outer Board: The complementary side of the home board.

P
Pip: A measurement unit for the distance between the board's points.
Pip Count: A total number of pips that a player must move his checkers, including bearing them off (167 at the beginning of a game).
Point: One of the twenty-four triangles on the board with alternate colors, where the checkers stay.
Prime: Six consecutive blocks belonging to a player, which stops the opponent's checkers.

Q
Quads: A roll of double four.

R
Race: A board position where neither player can hit or block the other.

S
Single Game: A finished game in which the losing player has borne off at least one checker or a game that ends when a double is refused.
Stake: The wager in a game of backgammon, doubled when the cube is passed and accepted.

T
Tric-trac: The French name for backgammon.
Triple Game: see Backgammon.

W
White: The color (light) for a player's checkers, or the opposite for black.