The +/- stat is tied to team performance during the time that that particular player is on the court. The games official scorer records the differential in terms of gain (plus) or loss (minus). By way of example, if David Lee enters the game with the score tied at 80 to 80, and leaves with his team ahead by 3, he gets a plus 3. Conversely, if he enters with his team ahead by 13, and leaves with a 3 point lead, he gets a minus-10.These numbers are added up throughout the game until at the end you have your final +/- for each player that you see in the box score.Read more: http://wiki.answers.com/Q/What_does_plus-minus_mean_in_basketball_box_score#ixzz1AxXo7rkd