Since the liquid will not compress and the cylinders are of the same diameter, the same amount of liquid is moved from one cylinder to the others. When pistons of different sizes are used, motion and force can be increased and increased. Suppose a small piston acts on a larger piston. The larger piston will move with more force. However it will move a shorter distance. When a larger diameter piston acts on a smaller piston the result will be opposite. The smaller piston slides faster in its cylinder hut with less force.
Apply these hydraulic principles to a brake system; you can see how a stopping force is transmitted from the master cylinder to each wheel brake assembly (wheel cylinder), The heel cylinders act as the power piston to move the friction lining in to contact with the rotating drums or discs.