Sportsbooks, anxious to offer as many betting options as possible to its customers, will typically offer wagers on game totals.  Many bettors will refer to this type bet as "the over under".  The game total is the combined scores of both teams in the contest.  The sportsbook will predict the combined final scores of both teams and the bettor can choose whether the actual final total score will be "over" or "under" the sportsbook's predicition. 

Frequently the sportsbook will predict a total score ending in a half point, such as 43.5.  As this exact final combined score is not possible, it eliminates the possibility of a tie or "push". 

Some sportsbooks will also add derivative bets from the total.  It is possible to find total bets for individuals teams.  Derivative total bets for first and second halves and even individual quarters can be found. 

The Sportsbook's Advantage

Once again, the sportsbook's advantage is the juice.  At -110 juice, the bettor must consistently pick 52.5% winners on his totals bets to stay ahead of the sportsbook.  If the book is posting a true total line, and the sports betting market is reasonably efficient, then getting an edge on totals can be difficult.  Not impossible, though, and some bettors make a career out of betting on totals and their derivatives.