A rugby league team consists of 13 players on the field, with 4 substitutes on the bench. Each of the 13 players is assigned a position, normally with a standardised number, which reflects their role in attack and defence, although players can take up any position at any time.
Players are divided into two general types, forwards and backs. Forwards are generally chosen for their size and strength. They are expected to run with the ball, to attack, and to make tackles. Forwards are required to improve the team's field position thus creating space and time for the backs. Backs are usually smaller and faster, though a big, fast player can be of advantage in the backs. Their roles require speed and ball-playing skills, rather than just strength, to take advantage of the field position gained by the forwards. Typically forwards tend to operate in the centre of the field, while backs operate nearer to the touch-lines, where more space can usually be found.