Don’s bet on this game was 2 Units on the Texas Rangers on the Run Line + 1.5 RUNS

We won the bet with the final score of Rangers 6 and the Red Sox 7.

So does the + 1.5 mean that we would have lost if the Sox beat us by 2 or more runs ?
And does – 1.5 mean the team we bet on would have to beat the opposing team by MORE than
1.5 Runs ?
If that’s true, why do we bet on a straight win no matter the score vs the + or – 1.5 runs figure ?

Thank you.
Saxman
PS: I’m not sure if this is where I’m supposed to post this Sports Betting question.