At the risk of asking a "dumb" question, what does it mean when I read the motor unloads in the air or loading the motor properly?

Thanks,

James

what does it mean when I read the motor unloads in the air

It means you're reading the right magazine?

Seriously, the prop resists the motor turning -- this the 'load' that is being referred to.  The more torque the prop absorbs, the more it is loading the motor.  As the aircraft reaches flying speed the propeller generates less lift at a given speed, and so absorbs less torque -- thus the load is removed, or the motor "unloads".

or loading the motor properly?

Any engine (or electric motor, for that matter) has a load and speed combination that is optimal, and a range of loads and speeds that will keep it healthy and happy.  You want to load the motor in such a way that it generates enough power, with a propeller that uses this power efficiently at the speed you want to fly, and without putting too much load on the motor (in which case it'll be down on power and may tend to overheat), or too little (in which case it'll be down on power and it'll run too fast).

Loading the motor properly is a matter of choosing the right propeller for the flying that you'll be doing.