Main feature difference of two stroke and four stroke internal cubustion engines?

a 4 stroke goes - intake, compression, power, exhaust.
a 2 stroke completes the same steps in only 2 strokes and fires the plug every time the piston reaches top. it does this by using the crankcase as part of the intake.
due to this you do not add oil to a two stroke - you either mix it in with the gas or some engines have self-oil systems.

4 strokes are more powerful the bigger the engine is.
2 strokes are more powerful at a smaller size.
I.E - a 50cc 2stroke will make more power than the same sized 4 stroke.
that is why they are used in weed trimmers, lawnmowers and scooters.