How do uploaders compress movies and games into small size?

Hello… I want to know how uploaders compress games and movies into small rar files. I downloaded 300-400 mb file size rar files and the quality of the movies is superb. Both some size movies and large size ones(800 mb or 1gb) have similar quality. My question how to they compress movies into small size. I have software called Total video convertor(i dont know how to use suitable codecs) but i cant compress movies into small size. Similarly how do they rip and compress games in 200 and 300 mb files ?
Answer #1
Codec: x264,h.264
Container: mp4,mkv
Check tutorial section here @ W-BB. They have a few tutorials on how to do it.