I am a programmer and therefor I just have to have control over what's happening under the cover on my computer.
Mac OS X is really Unix-based and when using the Terminal window you can use different commands from the Unix world to talk to your computer and make it do things under the cover. I am not really a Unix/Linux programmer, although I have had some experience in this. This made me look for a simple chart of some sort that shows the most simple commands accessible to me when using Terminal. I found a quite good pdf containing just what I needed. So now I am looking under the cover of Mac OS X. I don't really know I'll be doing, but maby I'll do some posting of stuff I do here.
You can view the pdf here.