The bookmaker functions as a market maker for sports wagers, most of which have a binary outcome: a team either wins or loses. The bookmaker accepts both wagers, and maintains a spread (the vigorish) which will ensure a profit regardless of the outcome of the wager. The Federal Wire Act of 1961 was an attempt by the US government to prevent illegal bookmaking.[2] However, this Act does not apply to other types of online gambling.[3] The Supreme Court has not ruled on the meaning of the Federal Wire Act as it pertains to online gambling.
As an illustration, let's look at Super Bowl futures. Sports books list each NFL team with corresponding odds to win the Super Bowl. For example, the Ravens may be 5-1, the Redskins 12-1, the Cardinals 100-1, etc. If you place $10 on the Redskins and they go on to win the Super Bowl, you collect $120 plus your $10 back for a total payoff of $130. It does not matter whether your team covers the point spread in the Super Bowl. For the purposes of future book betting, the team has to win only the Super Bowl.

The level of the gambler’s profit or loss will be determined by the stake size selected for the bet, multiplied by the number of unit points above or below the gambler’s bet level. This reflects the fundamental difference between sports spread betting and fixed odds sports betting in that both the level of winnings and level of losses are not fixed and can end up being many multiples of the original stake size selected.
Total: Also called the over/under, it is a number set by the sportsbooks that proposes a number of points that will be scored in the game by both teams combined. Then, fans predict whether there will be more points or less points than the ‘total.’ If you bet the under 41.5, you are hoping for a tough defensive battle with lots of running game. Pick the over, and presumably you feel this will be a high-scoring game. In short, you are predicting whether the combined total score will be more than (over) or less than (under) the total.