Bolt stick is pretty much what it sounds like. You go to pull the trigger, and nothing happens. You hear a puff of air, but the bolt is stuck and hasn't moved. Basically, what happens is the o-rings get stuck when they haven't been fired in a while. The force from the air pressure is usually enough to overcome this and the gun shoots normally, but in some guns, whether there's too much lube or not enough or it's got the wrong kind of lube, the stiction is greater than the air pressure can handle, and the bolt just sticks.
When properly lubed with the right stuff, bolt stick stops being an issue most of the time. Different bolts can change things by using less o-rings, adding or removing different forces and levels of force, etc.
The important thing to remember is lube your bolt properly, utilize the anti-FSDO settings on the gun's board, and that should solve bolt stick problems.
Edited by andrewthewookie, 24 August 2013 - 12:13 AM.