Sportsbooks also offer wagering on the total or Over/Under – the cumulative number of points scored by both teams in a game. You can bet on if the final score will go either Over or Under that set total. For example, in a game pitting Team A vs. Team B, the total is 48. A wager on Over wins if the total points scored exceeds 48, and a wager on Under wins if the total points scored falls below 48. If the total lands on 48, it’s a push and wagers are refunded.

In November 2014, a poll found that there had been a major shift in attitudes towards sports betting in the United States, showing that 55% of Americans now favored legal sports betting, while 66% of respondents agreed that this should be regulated by state laws, as opposed to federal legislation.[17] The poll also suggested that 33% of respondents disagreed with the notion of legalization.
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:

The team that has the minus sign, which is the favorite, has points deducted from its final score, while the dog, with the plus sign, has points added. The favorite must beat the spread, which means they have to win by more than the negative number to pay off. The underdog pays off in two instances—if they win outright or if they lose by less than the spread.
Identify the type of line you are looking at. All online sports books offer you the chance to have your lines in an "American" or "Money line" version. If I were you, I would use this as my standard. An "American" line uses either a + or - before a number to indicate odds. So a -120 and a +120 are two very different odds on a team… I will explain the differences shortly. Two other less common variations exist: decimal odds and fractional odds.
What's the difference between an oddsmaker and a bookie? A bookie's job is purely mechanical. He gets the line from Vegas or another source, offers bets at those odds, then collects money from the losers, pays out to the winners and keeps the vig. Oddsmakers don't actually take bets -- they study the games and set the lines. Bookies often adjust the spreads for their games, so they do a little oddsmaking, and oddsmakers work for casinos, which operate sports books that take bets.

Total: Also called the over/under, it is a number set by the sportsbooks that proposes a number of points that will be scored in the game by both teams combined. Then, fans predict whether there will be more points or less points than the ‘total.’ If you bet the under 41.5, you are hoping for a tough defensive battle with lots of running game. Pick the over, and presumably you feel this will be a high-scoring game. In short, you are predicting whether the combined total score will be more than (over) or less than (under) the total.