Those aren't 'Telnet' commands. There really aren't any 'Telnet' commands. Telnet is simply the protocol that gets you where you're going. In your case, it looks like you're connecting to a UNIX host, so you'll be needing a primer on the UNIX 'shell' (The UNIX equivalent of a DOS command prompt). I'd start with 'Unix in a Nutshell' You can get it here from Amazon:
http://www.amazon.com/exec/obidos/ASIN/1565924274
That'll be a good start. But, before you get going, you may want to check out the SSH protocol available in AbsoluteTelnet if you're connecting to remote machines over the internet. It's like telnet, but encrypted and secure, where telnet is very vulnerable because everything is sent as clear text (including your password).
As for rz and sz, those are commands implemented by the optional rz/sz file transfer package. Not all systems will have this installed, so you might need to talk to your sysadmins. Sometimes the rz and sz commands are named lrz and lsz, so you might want to look around a bit as well.