Betting on the total, or over/under (O/U), is a bet on the total scored by both teams.
In the example above, the total is 45.5 points. You can bet on more than 45.5 points scored in the game. This is betting on the “over”. You can also bet on less than 45.5 points scored, which would be betting on the “under”.
If you bet $105 on the under and 45.5 total points are scored by both teams combined, you would win $100.
If you bet $115 on the over and 45.5 points are scored, you would lose the bet.
If the total is a whole number such as 50, and exactly 50 points are scored you bet "pushes". This means your wager is returned since you did not win or lose the bet.