Why do you think water comes out of the tap? The water comes up into the tap from underneath. Water doesn't flow uphill by itself, so something must be pushing it. The answer is Pressure. The pressure is caused by the water in the yank above the tap. The route that the pipe takes from the tank to the tap doesn't takes from the tank to the tap. As long as the tank is above the tap, water will flow out.
The pressure in a liquid can be used to work machinery. The machine is called Hydraulic machines. A narrow syringe A, connected by a tube to a wider syringe B. They are filled with a liquid. What would happen if you pushed on piston A? The pressure is transmitted from one piston to the other, so piston B moves out a little bit. The pressure is the same at the both ends: at piston A it is caused by a small force acting over a small area. At piston B it exerts a larger force acting over the larger area. The force has been magnified. The formula is
force A/area A= Force B/ Area B.