Chess Software

Ok once and for all, what is the chess software people use, and more important, what do they use it for??? is it to play or to just ETERNALLY analyze games? Personally i like software i can play against in different levels, so i guess that would be chessmaster and co, but i hear that all the super duper kung fu ninja chess players use chess base, which works on fritz but runs rybka that can also use aquarium....

So whats chessbase for? just an expensive chess database??? is chess software at masterlevel ONLY used to analyze games???? if so, thats pretty dissapointing, i like to play against the machine at different levels as well as analyze.

Please comment.