Chess software

I know that this topic has been discussed zillions of times (but not by me). I have been reading about Chess software and cannot understand if Deep Rybka and Deep Fritz are the same or which is better or...(a million other questions). I want to learn to improve my game (naturally) and want to know what software can do for me, how does it work, and of course which is the best.

There is discussion on rybkaforum.net titled:

Rybka 4 As an analysis Chess Engine

EDIT: The discussion is too technical and focused on the imperfections of Rybka 4 compared to the previous version. Read my next post for another recommendation.

The best tool is useless unless one knows how to wield it.

Check out the book titled Modern Chess Analysis by Robin Smith. It will show you how to use any of the databases and engines for your opening preparation, middlegame analysis and endgame training.