The numbers rolled by the dice dictated how many spaces the player can move. If the roll is 1-6, the player can move two separate pieces one and six points or pips as they are referred to. The player could also advance a single piece by seven points.
One of the more well known backgammon rules is that in the event of rolling a double which means both dice show the same number the player has the ability to move four times the number shown on the dice and any combination of this. Hence the value of rolling a double-six.
If it was 3-3 the player has 12 points to play with which means moving two pieces six each or one three and one nine. He could move two three points each and one six or move four pieces three each.
