Telnet - Protocol
Telnet is the way you can access someone else's computer, assuming they have given you permission. (Such a computer is frequently called a host computer.) More technically, Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers. The Web or Hypertext Transfer Protocol protocol and the File Transfer Protocol protocol allow you to request specific files from remote computers, but not to actually be logon as a user of that computer. With Telnet, you log on as a regular user with whatever privileges you may have been granted to the specific application and data on that computer.
A Telnet command request looks like this (the computer name is made-up):
telnet the.libraryat.harvard.eduThe result of this request would be an invitation to log on with a userid and a prompt for a password. If accepted, you would be logged on like any user who used this computer every day.