Gravity accelerates an object. Air resistance slows it down. When the two effects balance out, you reach terminal velocity for that object dropped from that height.

Gravity acts on a feather and an iron cannon ball the same. Because of their difference of surface area ratio to weight (partly density but more than just that), these two objects have different terminal velicities.

One pound (or kilo - depending on where you live) MASS of both objects would reach the same velocity if subjected to the acceleration of earth's gravity in a vacuum.

An object that is attracted into the earth's gravity well, will have a maximimum theoretical terminal velocity (which is beyond me at the moment, but someone here will surely tell us!), which is modified by the above concepts discussed.

Robin