What is Exhaust and intake valve?

What is Exhaust and intake valve?
As an air/fuel mixture is drawn into the intake ports, intake valves open to allow the mixture to enter the cylinder. On the exhaust stroke of an engine, the exhaust valves open, allowing the burned air/fuel mixture to exit out the exhaust ports. Intake valves are larger than exhaust valves, and are able to be found on the "cold" or intake side of the cylinder head(s).