Point spreads are a way to "even up" a game matchup. For instance, if a very bad team is playing a very good team, the bad team is given points, so it becomes harder to select the winning team. This prevents pool members from automatically picking the best teams every week. Here is a small example: The Atlanta Falcons are playing the 49'ers. The 49'ers are favored by 12 points. The Falcons lose the game by 10 points. If you are running a point spread pool, the pool members who picked the Falcons are the winners, because the 49'ers did not win by more than 12 points.
Entering Point Spreads in the NFLPM:
To correctly enter point spreads, when you are entering point spreads, all fractions should be entered as decimals. In the Options screen, you are allowed to choose if you want to enter the point spreads next to the favorite or the underdog. In either event, always use a positive number. You do not need to enter negative numbers if you like to place the point spreads next to the favorite. If a game is a "tossup", then just leave both boxes blank. If you made mistakes on entering a point spread, you can return at any time to correct it.