There are full simulator controls for joystick and mouse control, everything you do is on you, nothing is interfering, no instructor, nothing.
the instructor is what controls your plane in anything but simulator and realistic, you simply point where you want him to go.
in realistic, you fly the plane yourself, but the instructor prevents you from crashing it due to pulling ridiculous turns or whatnot, he keeps you flying pretty much, so about 85% of the planes full capability.
in Sim, you're on your own. you can fly at 100% of your planes capability with all the ups and downs.