Spread - a.k.a. "point spread" or "line".  Probably the most common type of bet, a spread bet is one in which one of the teams must win by a certain margin for a bet on them to be a winner.  This is done to ensure there is action on both teams.  It is rare that any sporting contest is an evenly matched event.  One team is the favorite and the other the underdog.  The Sportsbooks require the favorite team to not only win, but cover the spread in order for a bet on that team to pay off.  

The favorite in a spread wager is indicated by a negative (-) sign in front of their spread, the underdog a positive (+) sign.  For example, if Pittsburgh is a 6.5 point favorite over Cleveland, the spread wager will read:

Pittsburgh (-6.5)

Cleveland (+6.5)

If you select Pittsburgh for this wager, Pittsburgh must win by 7 points or more (as half points are not possible in sporting events - which is why sportsbooks use them for spreads; it prevents ties between the book and the bettor).  If Pittsburgh wins by only 6 points, you lose your bet on Pittsburgh in this scenario.

A bettor may ask, “What is the line on the Pittsburgh game?”  The answer to that question would be, “Pittsburgh -6 and a half.” 

You may also hear a bettor ask, “How is Pittsburgh doing against the spread this season?”  This bettor is asking how often Pittsburgh covers (beats) the spread to make a winning bet in the current season.

THE SPORTSBOOK'S ADVANTAGE

On a spread bet the sportsbook's advantage is the juice or vig on the bet.  The sportsbook generally requires the bettor to risk slightly more than he or she can win from the bet.  The bettor is, in effect charged an extra fee for placing the bet.  This extra fee is commonly known as juice.  This way, if the book has balanced action then the winning bets pay the losing bets and the book keeps the juice.  This is discussed in greater detail elsewhere on the site.