An Open Letter to the Folks Who Fact Check Gun Reporting at the Associated Press
The action of a gun can be entirely manual, as is the case with a revolver where the force needed to pull back the trigger and hammer is what is putting the bullet into the gun chamber. (The gun chamber is the part of the gun that accepts the bullets or, in the case of a revolver, the chamber consists of the little holes where you insert the bullets before closing it and preparing to fire or conceal.)
The action of a gun can be semi-automatic, where there is some mechanical "help" putting the bullet in the chamber but which still requires a trigger pull for each bullet fired.
Or it can be an entirely automatic process where depressing the trigger will spray bullets out of the gun.
Shotguns do not fire bullets -- they fire shot shells, which are cartridges full of lead (or steel) pellets.
Feel free to ad your own advice for the AP in the comments.