A 1st Half NBA moneyline bet allows a bettor to wager on which team will win the first half without having to deal with a point spread. A win by any amount will cash the bet regardless of what the spread was.
Instead of a spread there are odds associated with each team to balance out the bet. If you are betting the favorite you will have to lay additional money while an underdog gets a additional winnings if they win outright.
1H Lakers -135 vs Mavericks +125. In this example the Lakers are -135 to win the 1st Half while the Mavericks are +125. You would have to bet $135 to win 100 if you bet the Lakers 1H while for the Mavericks you would win $125 off a $100 bet. The easy way to think about moneylines is the "-" is how much you need to bet to win $100 , while the "+" is how much you win off a $100 bet.