mass

Okay so... Lowly mechanical engineer speaking up here with a simple-ish explanation.

I don't want to throw out equations, so think of this intially. If you have an object floating in space just sitting there then it's just going to stay where it is.

If you introduce gravity into this situation, you're basically saying there is a force that the mass of this object produces...it's facing this way and it's going to make it fall faster and faster this way because the force is constant.

If you introduce something like air resistance then it's opposing that gravity force in the opposite direction.

Think of "Over the Top" with Sylvester Stallone. It's like two arm wrestlers... One is gravity and the other is Air resistance. Gravity force on you is called your weight-which is constant based on your mass. The opposing arm wrestler's force is based on your shape and how fast you're going. and that force is called drag. So if you're a fatty you may have a big drag force to combat gravity. Or if you're really long... it depends largely on area in on form or another, not on mass.

And if anyone wanted to know about "terminal velocity" that's when your down "weight force" is equal to your up "drag force" and you stop accelerating (speeding up or slowing down) and just keep hurdling towards the ground at whatever unsettling speed your fatty or skinny shape dictates.

Hope that helps!