Answer:
there is many different toilet tanks that use different fill valves but the concept is the same EXCEPT for pressure assist or (mostly in commercial buildings) flush valves which do not have toilet tanks. When water flows into the tank threw the open valve it begins to fill up the tank and while the tank is filling it is also raising the float which is connect to the valve and when the float raises to a set height it shuts of the fill valve by pressure from the float arm. Pressure assist toilets have pressure tanks inside the toilet tank and uses the pressure from the supply line to flush the bowl, I think they are the best toilets to buy if you don't mind the noise and if you have good water.