Without a points handicap, it would not make sense to pay both sides of a wager the same amount when it's clear that not all teams are on equal footing. In fact, it is entirely possible for a team to lose the game in real-life but still win a bet if they only lose by less than a set number of points. Vice versa, a team can win a game, but lose the wager if they do not win by more points than what was predicted.

The second number in our example (-110 for both teams) tells you how much you have to wager in order to win \$100. It’s an easy way to calculate how much you’ll win if your bet pays off, presented in units of \$100 at a time for simplicity’s sake. Most of the time, these two numbers will be the same, because oddsmakers want to set lines so that they get as much action on the underdog as on the favorite, guaranteeing them a profit. If a book gets a single bet of \$110 (by a customer hoping to win \$100) on the Cowboys and a single bet of \$110 on the Giants, it will have taken in \$220, but will only have to pay back \$210 to whichever customer wins the bet. That’s a guaranteed profit of \$10, and since sportsbooks take far more than a single bet in either direction, they stand to earn that seemingly small amount of profit many times over. The \$10 difference between what you wager and what you win is known as juice or vig in the sports betting industry, and it’s the way books earn their bread and butter.

# The -110 listed is the actual odds given for these bets, and the odds determine how much you win based on the amount of your wager. This is why the odds are often called the price of a bet. When you see -110 odds, you need to bet \$110 to win \$100. Of course, you don't need to literally bet \$110; that is just the ratio of the amount bet to the amount won. You can bet \$11 to win \$10, \$20 to win \$18.18, etc.

This is because bookmakers are in business to make a profit, so they effectively charge a commission for taking wagers. This commission is known as the vig, short for vigorish, and it's one of the ways that bookmakers stay profitable. They don't charge it just for points spreads and totals either, as it's built into the odds for every wager that they offer.
While most football fans have seen a point spread before, not everyone understands how they work. There’s a common misconception that the oddsmakers are trying to outsmart their customers by posting the spread and getting people to bet on the wrong side. At the same time, many bettors think that their goal is to “beat the bookie.” This is false; as mentioned, the sportsbook is incentivized to keep the action on either team as balanced as possible, in order to limit exposure.
Apply the spread. In point-spread betting, the actual final score of the game is only the starting point. Say Chicago beats Detroit 24-17. Because Chicago was the favorite, you subtract the point spread from its final score. That's the purpose of the minus sign in the spread. The spread was 6, so you take 6 points away from Chicago's point total, giving you an "adjusted" score of Chicago 18, Detroit 17. If you'd bet on Chicago, you'd have won the bet. Now, say Chicago won the game 20-17. Subtracting the 6 points from Chicago's total gives you a final score of Detroit 17, Chicago 14. If you'd bet on Chicago, you'd have lost.
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.
The point spread is a handicap placed on one team for betting purposes only, it has no place in the game itself. It's designed to give both teams an equal chance at winning in the context of wagers. Think of it this way: If last season's Super Bowl champion was playing a basement-dweller team that hadn't won a game all year, that's a shoo-in bet. Of course, you're going to take the Super Bowl champs, and in all likelihood, you're going to win. What's the fun in that? Even your bragging rights would be next to nil.
Once you understand how the NFL point spread works, you can make smarter choices when it comes to your NFL picks. The most important takeaway: It’s not you against the bookie. Think of NFL spread betting in terms of a marketplace, where customers tend to overvalue some teams and undervalue others. Figure out which teams those are, and you’ll find where the profit margin is.
Since more people wager on football than any other sports it’s usually the easiest game to figure out how to bet. If you don’t know what to do, you can probably ask anyone in the sports book for instructions. The people visiting the casino might not know everything but they can give you the basics. Here’s a fairly thorough look at the different ways you can wager on football in Las Vegas.
Each week we see the volatility in the pro football point spread market with opening spreads often but not always moving and closing at a different number. In general the movements are caused by the weight of money on one side or the other however injury rumors or confirmation of an injury to a key player, unrest in a particular NFL team's management or any number of other reasons can contribute to a point spread line being reassessed and changed by the sportsbooks. The question is often asked then, is it better to place your NFL point spread wager early on the opening lines or wait until the hour or two before kick off? There are certainly pros and cons for both which are discussed further in The Football Lines .com's When to Place Your NFL Bet article however ultimately there isn't a definitive right or wrong answer as varying NFL betting situations can require a different and flexible approach.
To show how this can be exploited, take a point spread of -8.5 at odds of -110. This is a 50/50 proposition. Let's assume you've purchased enough points to move the spread to -6.5 at odds of -150. Now, you'd win instead of lose 6.24% of the time they win by 8, and 6.59% of the time they win by 7. Add these together with the 50% from the original proposition, and we get 62.83%.
The NFL spread (betting point spreads is also known as betting ‘sides’ since you are picking one side to win the game) acknowledges that not all teams are created equal. If they were, we wouldn’t need NFL point spreads at all – teams would be so evenly matched that every game was a toss-up (or a pick em in football parlance). Simply picking the winner would be enough of a challenge.