Money line is referring to winning a bet straight up with out the point spread.
For example,
Houston vs. San Antonio, Game Houston +8
Houston vs. San Antonio, Game ML Houston
in the first case, you're giving Houston an additional 8 points for the game. If the game ends with San Antonio beating Houston 90-83. You would win the bet because Houston with the additional 8 points would win the game. However, if you picked Houston with the ML then you would've lost the bet because Houston fail to beat San Antonio straight up.