Piston rings are essential components of an internal combustion engine. They are circular metal rings that fit around the piston, which moves up and down within the cylinder. Their primary functions are to seal the combustion chamber, control oil consumption, and help transfer heat from the piston to the cylinder wall. Typically made from materials like cast iron or steel, piston rings come in different designs, including compression rings and oil control rings. Proper functioning of piston rings is crucial for engine efficiency, performance, and longevity, as they prevent leaks and maintain optimal pressure during the combustion process.