Mean while... back to the original question... Simply put, all engines; internal combustion, or even turbojet engines on aircraft, work with the same basic principal... suck and squeeze, blow and go... meaning fuel is "sucked" into the combustion chamber, squeezed (or compressed), ignited for power and the remnants (gases) are dumped overboard befoe starting all over again.
4 cycle (also called 4 stroke) simply means that all I'v just described takes four strokes of each piston to accomplish. The major difference is that the intake and exhaust strokes require complicated timing of valves opening and closing. Additionally, all the moving parts are lubricated by an engine driven oil pump and the oil is routed to various areas within the engine. Whereas a 2 cycle (2 stroke) engine accomplishes the same thing in only (wait for it) 2 strokes. There are no valves and the engine is lubricated by the oil that's suspended in the gas...
Simple as that. The two stroke engines are required to rev at higher RPM's to achieve power and so, relative to the 4 cycle engine, are less durable. Generally speaking, they are usually much smaller for lightweight applications (chainsaws, some lawnmowers, etc.)