The point spread, which is sometimes referred to as the “handicap”, is the number of points taken from the favorite, or given to the underdog, in order to open up the chances of either team winning the wager evenly. In most games, there’s usually a team that is more likely to win, based on a number of statistical factors. If the only kind of wager available was on who would win between a very strong team and a poor team, it wouldn’t be all that exciting. The point spread was designed to make betting much more interesting, since it allows a bet on the losing team to win you money. How? Let’s break down an example:
Money line bets are particularly attractive to square bettors when they are looking at underdogs. They see a nice high positive number and think that the payoff is significant enough to be worth the risk. Unfortunately, underdogs are underdogs for a reason, and it’s usually because they aren’t very good. However, when the right opportunity presents itself, a money line bet on an underdog can grow your bankroll quicker than betting favorites would.
Spreads are frequently, though not always, specified in half-point fractions to eliminate the possibility of a tie, known as a push. In the event of a push, the game is considered no action, and no money is won or lost. However, this is not a desirable outcome for the sports book, as they are forced to refund every bet, and although both the book and its bettors will be even, if the cost of overhead is taken into account, the book has actually lost money by taking bets on the event. Sports books are generally permitted to state "ties win" or "ties lose" to avoid the necessity of refunding every bet.
With money line bets the goal is to pick the outright winner of a game or event without the use of a point spread. While money line betting is available for sports where point spreads are used, they’re most popular in sports like baseball and soccer where very few points are scored. Money lines are also used for sports where points do not determine the winner or loser, as in auto racing or tennis.
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.