What are the 4 strokes of the 4 stroke cycle?

The 'strokes' refer to (1) intake (of fuel-air mixture into the cylinder head), the (2) compression of these gasses, the (3) ignition (or combustion) of the mixture to force the piston down in the cylinder and (4) exhaust of the burned gasses into the exhaust system.

These activities (or 'strokes') require the synchronization of the valves (opened and closed by the camshaft rotation) with the motion and position of the piston so that both intake and exhaust valves are closed when the piston rises to compress the gasses and open when the piston rises to expel the burned gasses. Intake valve(s) open to allow fuel-air into the cylinder and exhaust valve(s) open to allow the rising piston to force burned gasses into the exhaust system. Of course, the ignition system must send a spark to the plug at the correct time for this all to work.