What is the Internet

The Internet is a worldwide collection of thousands of computer networks  that can intercommunicate.  All of them speak the same “language,” namely the TCP/IP protocol suite.  Users of any of the Internet networks can reach users on any of the other networks.  The Internet started with the ARPANET, but now includes such networks as NSFNET, NEARNet, and others.  Many other networks, such as BITNET, are tied to the Internet but are not an integral part of it.  Approximately one million people use the Internet daily. 

The Internet communicates via gateways with other networks such as CompuServe, MCI Mail, BITNET, FIDONet, UUNET, and USENET.  The Internet has several component networks (which themselves include other networks):

•  CREN/CSNET 

•  DDN  (Defense Data Net )

•  ESNET (Energy Sciences Network)

•  NASA Science Internet

•  NSFNET  (National Science Foundation 
    Network)

•  Terrestrial Wideband Network 

FTP:

The File Transfer Protocol (FTP) is the Internet standard protocol for moving files from one computer to another.  You can use the ftp command to copy computer files containing a variety of kinds of information, such as software, documentation, or maps.  FTP is the name not only of the protocol, but usually also of the program the user invokes to execute it (e.g., by typing ftp host.bbn.com).  FTP is available on several operating systems.

Telnet:

Telnet is a program that allows a computer user at one site to work on a computer at another site.  It is the Internet standard protocol for remote terminal connection service.   
             
Telnet requires Internet access (that is, you must be on a network that gateways to the Internet).  Unlike FTP and electronic mail, telnet exposes you to the commands and programs of the remote host.
             
For example, you can use the telnet command to run a program in your directory on a supercomputer hundreds of miles away.