Lets get this clear here:
Do you just want to know how to use the terminal app?
If so, there is no simple answer to that.
However a decent unix or Linux book (there are no decent OSX books yet, to my knowledge), of which there are loads, will get you started. There is also a lot of info available on the web. Or search this site and see what you can pick up.
Very very simply, the Terminal, like Aqua, is an interface. It is a command line interface (CLI). You can, for instance, view a listing of files on your disk and copy,move & delete them using the CLI. You can also run applications in it. If you have ever used DOS (god forbid) you have an idea.
spike.