Small Engines (Lawn Mowers, etc.): 2 stroke vs 4 stroke, 4 stroke engines, move down

Question
I have more than one question but I need to first understand what the difference is between 2 stroke and 4 stroke engines and why are they called that instead of something more understandable?

Answer
The rotation of the crank moves a piston up and down, the move up is considered a stroke, as well as the move down.
The two stroke is called that because the whole process of intaking the fuel/air, compressing, firing, and exhausting, are all accomplished in these two strokes, while a 4 stroke, the first down
and up movement sucks in the fuel/air and compresses it, the final
2 strokes deliver the power and expell the exhaust.

   Two strokes are inherently more pollutive, which is why the epa is regulating them out of existance.

Sorry about the simple explanation, It is how I understand it, why they called things that way, I don't know.

Fish