If you're a beginner in sports betting, the two things you want to understand are the odds and the terminology. The terminology begins with the over/under or the total.
"Over/Under or Total"
The over/under is the combined points between both teams in a game, a bettor may choose that the teams will score more or less than that number
For example, Team A is playing Team B, the total (or the over/under) is set at 39.5. The bettor chooses to bet the over, meaning that both teams combined score at the end of the game must be 40 or more. If the final score is 28-14, the bettor will win. If the final score was 28-10, the bettor would lose.
Vegas sets the lines so that odds are even on both sides of the number, similar to how they set the number for the spread. Odds for betting on either side of the over/under are normally at -110 (bet $11 to win $10).