RE: what does squeeze the trigger mean?
Here's another take: your goal in squeezing the trigger is to cause it to move directly to the rear. If you have your finger hooked over the trigger, even a squeeze can cause pressure to the right or left, thus affecting your sight alignment and sight picture. Ideally you should use the pad of your finger trigger. Jeff Cooper described the motion as 'pressing' the trigger, v. squeezing it.
And Semper Fi, driftrider.