Total bets are bets placed on the overall score of any given game, no matter who wins the game, you basically have to guess whether the total score of both teams combined will be "over" or "under" a specific number set by the bookmaker.
Over +22.0 -120
Under +22.0 -120
In this example the bookmaker has set the over/under figure at 22, so the oddsmaker believes there will be about 22 points scored in total.
If a bettor thinks there will be more than 22 points scored in the game, they bet the Over. If a bettor thinks that the there will be less than 22 points scored in the game, they bet the under. If the total is exactly 22 points, then the bet is deemed a push. All bets are voided and the stakes returned in this instance.
The second figure (-120) is the price of a winning bet, a winning bettor will win $120 for every $100 bet.
Total Bets are basically a variation of the standard straight bet with the added twist of the total score.