A spread line is the option to bet on the point difference between two teams. For example:
For Team A, the spread is -3 (making them the favorite), which means they need to win by more than 3 points to cover the spread and win the bet.
For Team B, the spread is +3 (making them the underdog), which means to win a bet on them, they cannot lose by more than 3 points.
If the favored team wins by exactly 3 points, all bets placed at minus or plus 3 will result in "no action", meaning the bets are canceled and the funds returned to your account.
The standard cost of straight bets on the point spread is 10/11, or $110 to win $100. But there are exceptions to this so please check all lines before making your bets.