With NFL odds the over/under can vary but usually it’s somewhere between 35 and 47 points. Let’s say in the Colts and Bengals game that the total is posted at 37.5. If Indy scores 27 and Cincy gets 13 points, the total would be at 40 and the over would win. But if the Colts rack up 35, and they shut out the Bengals, the total of 35 would be under.
A point spread (or line) is a tool used by sportsbooks to attract wagers on both sides of a game. The line is most commonly used in football and basketball games. Because it’s rare for two teams in a pro sports game to be completely evenly-matched, one team will have an advantage, another will be seen as the underdog. The point spread is the handicap offered to the underdog to level the playing field, so to speak.
Apply the money line. It's easiest to think of money lines in relation to $100. A minus sign means you have to bet that much money in order to win $100; a plus sign means that a $100 bet will return that much money. If you bet on Chicago at -110, you'll have to wager $110 in order to get back $100 (plus your original $110). If you bet on Detroit at +145, then a $100 bet will give you $145 (plus your original $100).
It’s common knowledge among bettors that the online gambling industry pays close attention to Las Vegas Sports Consultants, a private company that handles the odds for casinos and newspapers. But the totals I set have to reflect our customers’ preferences for betting the over or under on certain teams in certain situations. Also, because LVSC lines are published early, I have to keep on top of injuries and potential changes in coaching strategy leading up to the game in question before I release any totals. This is doubly important in basketball, where pace determines how many shots will be taken in 48 minutes.
Let’s say that the Mavericks and the Magic are playing in an upcoming game, and both teams are equal counterparts. Let’s say that the odds for that game are as follows. You will never see these odds, though, because in this example, the sportsbook is not set to make any money if they achieve their goal of getting money on both sides of the bet. But we need to look at it for you to better understand things.

If you like favorites, you're going to be betting a lot to win a little. The money line will always be listed to the right of the point spread on the odds board in a sports book. In the above example, the money line would probably be Chicago -250 and Detroit +200. To bet Chicago simply to win, you must wager $250 to win $100, while a $100 bet on Detroit would pay $200 if the Lions come through. 

Bookmakers use odds to even out the bets, getting gamblers to wager on both sides of the line by leveling the playing field. Although there is overall parity in the NFL, there are teams that are haves and others that are have-nots. Indianapolis is still superior to Cincinnati but when they play each other the bookies have to get about half of the bettors to put cash on the Bengals. This covers the sportsbooks ensuring they’ll make a decent amount of cash on just about every game.
If you want to predict what will happen when Team A meets Team B, your best stats to analyze are those generated in their most recent head-to-head matchups at the same venue. The habits of the betting public are fairly constant, so ATS results in general have a longer shelf life, but don’t bother going too far back in time. The 2009 New York Yankees are going to look a lot different than the 2008 Yankees or the 2000 Yankees. (Source: The Sports Bookie Blog)

Betting “against the spread” (ATS) just means you’re betting on the point spread in a particular matchup as opposed to the moneyline, or some other type of wager. Bettors often use a team’s ATS record to gauge its performance against the spread. For example, the New England Patriots were 11-5 ATS in the 2017 regular season, meaning they covered the posted point spread 11 times, and failed to cover five times.
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