PuTTY is a very useful tool, a small freeware implementation of Telnet and SSH for Win32 platforms, along with an xterm terminal emulator.

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.

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. The system prints a prompt, and you type commands which the system will obey.

Using this type of interface, there is no need for you to be sitting at the same machine you are typing commands to. The commands, and responses, can be sent over a network, so you can sit at one computer and give commands to another one, or even to more than one.

SSH, Telnet and Rlogin are _network protocols_ that allow you to do this. On the computer you sit at, you run a _client_, which makes a network connection to the other computer (the _server_). The network connection carries your keystrokes and commands from the client to the server, and carries the server's responses back to you.

These protocols can also be used for other types of keyboard-based interactive session. In particular, there are a lot of bulletin boards, talker systems and MUDs (Multi-User Dungeons) which support access using Telnet. There are even a few that support SSH.

LEGAL WARNING: Use of PuTTY, PSCP, PSFTP and Plink is illegal in countries where encryption is outlawed. I believe it is legal to use PuTTY, PSCP, PSFTP and Plink in England and many other countries, but I am not a lawyer and so if in doubt you should seek legal advice before downloading it. You may find this site useful (it's a survey of cryptography laws in many countries) but I can't vouch for its correctness.