in a simple word is you don't set a fixed amount of shots to capture.
and how many shots you shoot is really depends on what types people you met,
some will tell you if you have gotten the shots you want, you may stop there,
but some will want you to shoot until they can see smoke come out from your camera shutter than they allow you to stop.
Its an old term used during the transition from film to digital, when early digital photographers can offer 'unlimited' shots vs film photographers charges by the frame or roll.
Now with digital being the norm and the standard, when this term is used, it usually just mean cheap photography by photographers who have to use unlimited volume as a means to build value, or by clients who don't trust the low end photographers to deliver good shots and hoping that with a high volume they may fish out a few lucky shots.