The most basic use of SSH is as a replacement for telnet and rsh. At a command prompt, just type "ssh hostname.com" instead of "telnet hostname.com". This will only work if hostname.com has the SSH server software installed. We encourage you, if you're a system administrator, to turn off your telnet servers, and switch completely over to SSH.
Login can be set up in two ways, either using a PGP key, or plain password. Either way, SSH never passes anything in the clear: two way handshaking and exchange of session crypto keys takes place before any passwords or passphrases are sent. After you send your password, the session behaves more or less like telnet, but it's encrypted at all times. SSH behaves in the same manner as rsh, in that it assumes your login name on the remote server is the same as on the local one. To override this behaviour, use something like this:
root@localhost$ ssh remotehost -l giles