NBA Lines Explained: the numbers you see here on the right are called "lines" or sometimes referred to as "odds". The NBA lines are essentially the predictions of the odds makers about the basketball games. The lines with the minus sign in front of them are the favorite while the ones with the plus sign are the underdog. Simply said, you can see which basketball team is favored by the odds makers to win and which would be likely to lose by looking at the NBA lines and determining which one has the "-" and which one has the "+" signs in front of them respectively.