Telnet, short for TELecommunications NETwork, refers to both the application and the protocol itself, granting the name a dual role. Telnet provides users a way to log in and directly access their terminal across a network. This means actual, direct access to the remotely located computer. Telnet is provided on port 23.
Telnet requires that a Telnet server be located on the host machine, awaiting an authenticated login session from a remote location. Windows 9x/NT/2000, the BeOS, Linux, and other x86 platformbased operating systems require that a Telnet server be installed, configured, and running to accept incoming sessions. MacOS-based systems also require a Telnet server. Unix-based computers are the only systems that come with one and typically use an application called telnetd (the "d" denotes daemon, a server application). On the other end is a Telnet application that acts as an interface, either text-based or a GUI, for the session.
Windows 2000 actually has a CLI Telnet application built in. If you click on a Telnet link or type Telnet in the console, it will appear. Therefore, Windows 2000 no longer requires the addition of a third-party Telnet server.