If you see -105 for the game listed by a bookmaker on an NBA game, it is referring to two different types of wagers. One is a moneyline bet in which you are simply picking the winner. The other is a spread bet in which you are also picking the final margin of victory.
In a moneyline bet, if you see the minus (-) sign next to a team's name, this means it is the favorite. In this type of bet, it means you would have to wager $105 on the favorite team to win $100. As a point of reference, a -105 line is indicative that the oddsmakers consider the team to be a very slight favorite. In most games, the number will be higher, i.e. something like -110 or -150.
With a spread bet, a -105 also means you will have to wager $105 to win $100. The difference is you are not only picking the winner of the game, but you are also picking it to win by a larger number of points than the bookmakers have set as the spread line.
In spread bets, the oddsmakers are handicapping the game by selecting a margin of victory to make the teams equal and attract bets for both the underdog and favorite. A spread bet is only available for sports in which a game can not end in a tie. Since basketball always has a winner and loser, you can make spread bets on an NBA game. Since the bookmakers have made the teams "equal'' with a spread line by adjusting it to attract an equal amount of betting on each team, the line will appear as -105 or -110. For instance, if the New York Knicks were favored to win a game by eight points, the bookmakers would list it as New York Knicks -8 @ -105.
Among the factors bettors might want to consider with NBA bets are how the teams have been playing lately, injuries or recent trades and how the teams have usually fared against each other. There are times when one team might need to win the game more than the other in terms of improving their position in the standings to get a higher seed in the playoffs or qualify for the playoffs at all.
Most spread lines also include a .5 after the whole number such as 8.5. This is to make sure there are winners and losers with each bet. Should a game be listed as a + or - 8, if the final score is eight points the bet ends as a tie. This is what's known as a push and when that happens bettors will receive their money back.
A game listed at -105 is fairly unusual. It's much more common to see it posted at -110 where you would have to wager $110 to make $100. Called the vig, the 10 is added on so bookmakers can pocket the $10 and assure themselves of a profit.