A spread is a handicap applied to a match for betting purposes. The favourite is always indicated by a minus sign (e.g. -10.5) and the underdog by a plus sign (e.g. +10.5).
For betting purposes, the spread is the number of points added to or subtracted from a team’s final score at the end of the match. If you placed a -10.5 spread bet on a basketball team, your bet would win if your team won by 11 or more points. If they won by less than 10 points or had lost the game, the bet would lose.