4 stroke means it takes 4 piston strokes to make 1 power cycle. 2 stroke means it takes 2 strokes to complete 1 power cycle. 2 strokes require oil injection or premix and have no valve train (read simple).
2 strokes make power very differently than do 4s.
[video=youtube;hV3LImCslpo]https://www.youtube.com/watch?v=hV3LImCslpo[/video]