Multi-user operating systems, such as Unix and VMS, usually present a command-line interface to the user, much like the `Command Prompt' or `MS-DOS Prompt' in Windows. SSH, Telnet and Rlogin are three ways of doing the same thing: logging in to a multi-user computer from another computer, over a network.
PuTTY is a very useful tool, a small freeware implementation of Telnet and SSH for Win32 platforms, along with an xterm terminal emulator.
