A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders, and pneumatic cylinders, among other similar mechanisms. It is a moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft via a piston rod and/or connecting rod. In a pump, the function is reversed, and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder.
A piston is a key component in a reciprocating engine. Its made from a cylindrical piece of metal with piston rings that help to form an air-tight seal once the piston is installed within the engine cylinder. The piston is attached via a piston pin or gudgeon to a connecting rod, which in turn is connected to the crankshaft. In four-stroke (petrol and diesel) car engines, the intake, compression, combustion, and exhaust process takes place above the piston in the cylinder head, which forces the piston to move up and down (or in and out in a horizontally opposed - or flat - engine) within the cylinder, which causes the crankshaft to turn.
A piston is pretty much just a solid cylinder of metal that moves up and down in a similarly cylindrical hollow in the engine block. The piston itself is slightly smaller than the tube it moves in but is banded by piston rings under tension that manage to achieve a nearly air-tight seal against the inner side of this 'barrel'. The piston is attached via a wrist pin to a connecting rod, which in turn is connected to the crankshaft, and together they turn the up and down (reciprocating) motion into round and round (rotational) motion to drive the wheels.
A piston converts the energy released during combustion into a mechanical action and transfers it to the crankshaft in the form of a torsional force via the piston pin and the connecting rod. When the engine is running, the piston moves up and down in the cylinder. When the piston reaches the turning point, it slows down and then accelerates again suddenly. This produces inertia forces that act on the piston. When considered together with the forces generated by the gas pressure, this forms the piston force, which is transferred to the connecting rod and crankshaft.
