In addition to the spread bet, a very common "side bet" on an event is the total (commonly called the over/under or O/U) bet. This is a bet on the total number of points scored by both teams. Suppose team A is playing team B and the total is set at 44.5 points. If the final score is team A 24, team B 17, the total is 41 and bettors who took the under will win. If the final score is team A 30, team B 31, the total is 61 and bettors who took the over will win. The total is popular because it allows gamblers to bet on their overall perception of the game (e.g., a high-scoring offensive show or a defensive battle) without needing to pick the actual winner.
Having a choice between the money line and the point spread gives the bettor more options. Consider a scenario where there is a strong favorite for a game. You might want to guarantee a smaller return by betting on the favorite to win on the money line – or you might want to almost double your money by betting on that team to not only win, but win by more than a certain margin. Conversely by backing the dog, on the money line you’ll receive a better return for your money but by backing the same team against the spread you have the insurance of still being able to win even if the team don’t.
That was all before Charles McNeil, a math teacher from Chicago, invented the concept of the point spread. An avid gambler, McNeil created what he called “wholesaling odds” and started his own bookmaking operation in the 1940s. He started out offering this new style of betting on football, but his business model grew to include basketball.  McNeil changed the way sports betting was done, and his legacy lives on today in what we now call the point spread.