An internal combustion engine where it is the piston that complete all the 4 separate stokes while a crankshaft is turned is known as Four stroke engine or Four cycle. A stroke is referred to as complete traveling of piston along cylinder area in various directions.
There are 4 strokes in this regard:
The piston stroke begins at the top center and ends at the bottom center. Valve has to be in the open position and cylinder through its downward motion.
It is the ignition and starts off when crankshaft has completed the 360 degree revolution
The air-fuel mixture is compressed in this format and both intake and exhaust valves are closed.
It is the outlet that is used for expelling air-fuel mixture.
Stage 1 Suction Stroke (Process A-1)
Stage 2 (Compression Stroke) (Process 1-2)
Stage 3 Expansion Stroke (Process 3- 4)
Stage 4 Exhaust Stroke (Process 1-A)