The point spread is a number the odds-makers come up with in order to level the playing field of the two opposing teams. Bet Profit Suite
Basically, the favored team will be spotting the underdog a certain amount of points. In order for those who bet on the favorite to win their wager, the favorite must win the game by more than the point spread. If the favorite wins the game by fewer points than the point spread or lose the game altogether, those that wagered on the underdog would win their bet.
Here is an example of how to bet the point spread on a football game. Let's say the Colts are seven point favorites versus the 49ers. If you backed the Colts (-7) they would have to win the game by at least eight points in order for your wager to be a winner. Conversely, if you bet on the 49ers (+7), the 49ers would need to lose the game by no more than six points to win the wager. If the 49ers ended up beating the Colts outright, the 49ers (+7) wager would also be a winner. Finally, if the Colts won the game by exactly seven points, the wager would be considered a 'push' and you would have you wager refunded, or 'no actioned'.