When you wager on sports at a sports book you are going to see a lot of different numbers and symbols, and these are the “odds.” There is usually a difference in probability of victory between the opponents, and the odds provide a way to make it equally enticing to bet the team that is considered to be less likely to win. This is done one of two ways: either through the use of a point spread, or through what American sports books call the “money line.” The equivalent to the American money line that is used in English and Irish sports books are fractional odds; in other parts of Europe and throughout Canada and Australia, they tend to use decimal odds.
Points spreads present the simplest form of wagering against the odds. The oddsmakers look at the matchup and come up with a prediction of sorts. They consider the overall difference in quality between the teams involved coupled with the inherent advantage that the home team enjoys, and they come up with a betting line. So when you see that a team is -7 versus an opponent, that means that they are “giving away” seven points. The oddsmakers have decided that this team should logically win the game by seven points based on their analysis. If you bet on this team, you are “laying the points,” meaning that you win your bet only if the team wins by more than seven points. If they win by exactly seven points, the game is considered a “push,” and the money wagered is refunded to anyone who bet either side.
A lot of people think that they are betting against the sports book when they place a bet, but the fact is that they are really wagering against other players. Once the “opening line” was been decided and posted, the sports books will adjust it as the bets come in. If more people bet on that seven point favorite than are betting on their opponent, who would be “getting” seven points, the oddsmaker will adjust the line to try to entice more people to bet on the underdog. The line may go up to 7 1/2 or eight points.
The goal of the linesmaker is to balance the action. Sports books make their profit through collecting what is called the vigorish, often called the juice or just the “vig.” When you bet against a point spread, you have to lay out $11 to win $10–that extra dollar is the vig, and that is how the sports book makes a profit. The sports book wants a sure thing; they don’t want to gamble. So the ideal for them is to take an equal amount of bets on either side of a game so they rake in the vigorish without being exposed to any losses. This is why they constantly adjust the lines to try to even out the action.
Fractional odds, decimal odds, and the money line do not use a point spread. They provide either a positive or negative return as a way to balance the action. In other words, the favorite in a baseball game may be -200. This means that you would have to bet $200 to win $100 (half of your bet). Using decimal odds, this same ratio would be posted as 1.50; using fractional odds it would read 1/2. Depending on the rules of the sportsbook, the underdog in this same baseball game may have a line of +185, meaning you would win $185 if you bet $100 on this team and they won. Now you may ask why you don’t you win $200 betting on the underdog since the favorite is -200? That difference is the vigorish that keeps the sports books in business.