What are you trying to achieve here? It would be easier first think of something that you want to do and then find out a way to do it. Asking for "all the commands for xterm" is like asking for all the programs for Windows.

If you just want to learn to use the command line, be creative, use google This site seems to be a nice place to start.

Oh and you shouldn't really be using telnet for anything in this day and age