A Piston is a Component of Reciprocating Engine (Combustion Engines), Reciprocating Pumps, Compressor, And Pneumatic Cylinders, Among Other Similar Mechanism.
It is the Moving Component That IS Contained by a Cylinder and is Made Gas-Tight by Piston Rings, In an Engine, and its purposes to transfer Force from Expanding Gas in the Cylinder to the Camshaft via Connecting Rod.