I THINK - that what you want is called a Walking Foot machine. On a normal light-duty home machine, the fabric is advanced by a serrated piece set in the bed of the machine that grabs the fabric, pressing it upwards against the presser foot, and moves it forward (or back) one stitch.
In a walking foot machine, the presser foot also moves along with the serrated piece, reducing friction and allowing the use of heavier fabric or leather. On some machines, there are two presser feet, which walk alternately.
I could be wrong about some of this, but you can probably find nice close-ups of machines in action on youtube, or where I've seen it is in the car customizing shows on TV, where they frequently show the custom upholsterers in enough detail you can see the action of their sewing machines.
Oh, and bring money.