In this example, we have a favorite to win, and an underdog. The Packers are the favorites, and that is shown by the (–) value in front of the 6. Underdogs are represented by the (+) value.  The 6 point value is how many points either team could win, or lose by. If you think the Packers will win by MORE than 6 points, then you’d bet on the favorite in this case, meaning that the Packers have to win by 7 or more points in order for you to win your bet.
For each NFL game the oddsmakers set a number of points in which the favored team is favored by. Bettors can then either choose for the favored team to win by more than the number of points set, or bet on the underdogs to lose by less than the number of points they are underdogs by or win the game straight up. For example, the spread could be set on the favored team at 6.5 points. This would mean in order for a bet on the favored team on the spread to win they would need to win by more than 6.5 points (7 or more) in order to win the bet. It also means that a bet on the underdog team would win if the underdogs lost by less than 6.5 points (6 or less) or won the game outright.
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.
The National Basketball Association (NBA) has always been a staple of the sports betting community. As a part of one of the big four sports, bettors have been working to develop systems to best the basketball betting industry for decades. Some have succeeded and enjoyed the spoils, while some have fallen. Our guess is that most of those who have fallen did so due to a lack of effort, a lack of information, or just no knack for the sport.
Remember that every spread still has a moneyline attached to it. While that might be a bit confusing, all that refers to is the cost of betting the spread; not how the outcome will be decided. For example, if someone says to you that “the Patriots are laying three points but I have low juice, so my moneyline is -104”, what they are referring to is the price of betting the spread. That merely means that they are betting the spread but the moneyline attached to betting that spread is -104.
Bets on “Winner of Point”, “Scorer of Goal" and similar offers refer to the participant winning the listed occurrence. For the settlement of these offers, no reference to events happening prior to the listed occurrence will be taken into consideration. Should the listed event not be won within the stipulated time frame, all bets will be declared void, unless otherwise stated.
NFL games are popular moneyline games because the specific outcomes can sometimes be difficult to predict for casual players.  Moneyline games are also profitable when they win, which is one reason why the NFL is a favorite among sports gamblers.  An example of a money line is: New York Giants (-120) vs. New Orleans Saints (+130).  In this game, a bet of $120 on the Giants is necessary to win $100, while a bet of $100 would win $130 in the case of a Saints win.  The team with the minus sign is the favorite and indicates how much a player must put down in order to win $100.  The team with the plus sign is the underdog and indicates how much a player would win for a bet of $100.
With some betting sites odds, certain games are priced differently than risking $1.10 to win $1.00 (which is called -110 odds). For example, you might see the Giants priced at -105 and +7 in a game against the Jets. Now, you only have to risk $1.05 to win $1.00. This is obviously better odds, but it's very likely that they will lose by exactly seven to give you a push. Taking -110 and +7.5 with an alternative bookmaker is actually the better bet.

Reading sports betting lines becomes easier with practice and experience with different sporting events. What looks like a jumble of letters and numbers actually gives a lot of information in a tiny amount of space. Different sports have different types of wagers available, such as the run line in baseball or the puck line in hockey, both of which replace the money line found in our football example. The more experience you have watching and gambling on different sports, the faster you’ll be able to read betting lines.

Notice that point spreads adjust the score for the favorite team. This is easiest to see with an example: If the New York Knicks are playing the Boston Celtics, and Boston is favored to win by a 4-point spread, then a bet on Boston only pays out if Boston wins by more than 4 points. A bet on New York pays out if New York wins or if they lose by less than 4 points.
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.