A teaser is a bet that alters the spread in the gambler's favor by a predetermined margin – in American football the teaser margin is often six points. For example, if the line is 3.5 points and bettors want to place a teaser bet on the underdog, they take 9.5 points instead; a teaser bet on the favorite would mean that the gambler takes 2.5 points instead of having to give the 3.5. In return for the additional points, the payout if the gambler wins is less than even money, or the gambler must wager on more than one event and both events must win. In this way it is very similar to a parlay. At some establishments, the "reverse teaser" also exists, which alters the spread against the gambler, who gets paid at more than evens if the bet wins.

Sports betting would be easy — or maybe just easier — if all that was required was to correctly pick the winning team. Gambling institutions, sportsbooks and bookies fall back on point spreads to make the process a little more difficult and to create the ultimate wagering challenge. You'll need a solid understanding of the point spread system if you hope to have a profitable season.
--Fractional odds are most commonly found in racing. A 10/1 payout should be read "$10 paid for every $1 wagered." When the bigger number is on the left, you will find that bet is normally an underdog in the race. Also note, however, that in case such as "Who will win the Super Bowl in the NFL?" you will see all the teams listed as "underdogs"… i.e. paying at least 2/1 (some up to 300/1 or more).
Sports betting has been around since 1000 B.C in China, where betting on animal fights was commonplace. In ancient Rome, one could wager on the Gladiatorial games. The idea of betting on sports is as old as organized sport itself. But up until the 1940s, bettors were fairly limited in what kind of bets they could make. The standard system of odds would allow bets on, for example, the 3-1 odds that the Steelers would beat the Browns.