Question

Within an internal combustion engine, the can-shaped component that moves up and down the cylinder

Answer 1

This component is called the piston.

A piston is a cylindrical engine component that slides back and fourth in the cylinder bore by forces produced during the combustion process. The piston acts as a movable end of the combustion  chamber.

Pistons are commonly made of a cast aluminum alloy for excellent and light weight thermal conductivity. Aluminum expands when heated and proper clearance must be provided to maintain  free piston movement in the cylinder.

If the clearance is not sufficient the piston will seize and if it is excessive there will be loss of compression.