The term telnet also refers to software which implements the client part of the protocol. TELNET clients have been available on most Unix systems for many years and are available for virtually all platforms. Most network equipment and OSs with a TCP/IP stack support some kind of TELNET service server for their remote configuration (including ones based on Windows NT). However with recent advancements SSH has become more dominant in remote access for Unix-based machines.
"To telnet" is also used as a verb meaning to establish or use a TELNET or other TCP connection, as in, "To change your password, telnet to the server and run the passwd command".
Most often, a user will be telneting to a unix-like server system or a simple network device such as a switch. For example, a user might "telnet in from home to check his mail at school". In doing so, he would be using a telnet client to connect from his computer to one of his servers. Once the connection is established, he would then log in with his account information and execute operating system commands remotely on that computer, such as ls or cd.
On many systems, the client may also be used to make interactive raw-TCP sessions.