Definition: Internet

The term internet (lower case "i") always meant a large network made up of smaller networks. Today, the term mostly refers to the global Internet, spelled with upper case "I" in this encyclopedia.

Indispensable to the World Economy
As of 2025, more than five billion people use the Internet in approximately 200 countries, and trillions of requests are made to the Internet every single day from users and automated software (see bot).

As the countries with the three largest populations, China, India and the U.S. have the most users. Originally developed for the U.S. military, before it became public, the Internet was used for academic research with access to unpublished journals on many subjects.

Access Was Command Driven
Before the Web and graphics-based browsers, academicians and scientists accessed the Internet using command-driven Unix utilities. Some of these utilities are still used for all platforms. For example, FTP (file transfer program) is used to upload and download files, and Telnet lets a user log in to a computer and run a program. See FTP, Telnet, Archie, Gopher and Veronica.

A Distributed Network
Not only is the "Net" the largest source of information on every subject known to humankind, it has unfortunately become the greatest source of misinformation and disinformation (see social media). The highest traffic over the Internet is video streaming followed by everything else, including websites, email, voice, chat, backup, app updating and machine-to-machine communications.

Unless restricted by company policy or authoritarian governments, every stationary or mobile device connected to the Internet can communicate with any other on the planet. Interconnected by major backbones, the Internet relies on multiple autonomous networks for its operation. In fact, its distributed design was chosen to eliminate the possibility of an attack on a centrally controlled network that would render it inoperable.

Email Lit the Fuse
In the mid-1990s, the Internet surged in growth, increasing a hundredfold in 1995 and 1996 alone. The first reason was email. Until then, online services, such as AOL and CompuServe, provided email only to their customers. As they began to interface with the Internet's mail system, the Internet became a global email gateway. For the first time, AOL members could send messages to CompuServe members, and vice versa. The Internet glued the world together for email and then for everything else.

The Bomb Exploded with the Web
With the advent of graphics-based Web browsers such as Mosaic, Netscape Navigator and Microsoft's Internet Explorer, the World Wide Web took off. The Web became available to users with PCs and Macs rather than only to scientists at Unix workstations. Delphi was the first proprietary online service to offer Web access, and the others followed. Coming out of the woodwork, Internet service providers (ISPs) offered access to everyone, and the Web grew exponentially, soon becoming the majority of Internet traffic. Later, video streaming superseded Web pages. See ISP, HTTP and HTML.

Newsgroups and Chat Rooms
Although daily news and information is available on countless websites, long before the Web, information on myriad subjects was exchanged via User Network newsgroups (see Usenet). Still around, newsgroup articles can be selected and read directly from a Web browser.

Chat rooms provide another popular Internet service. Internet Relay Chat (see IRC) was the first and is still around; however, Facebook Messenger, WhatsApp and Discord offer interactive discussions on every topic for millions of people.

The Original Internet
The Internet started in 1969 as ARPAnet, funded by the U.S. government. ARPAnet became a series of high-speed links between educational and research institutions worldwide, although mostly in the U.S. A major part of its backbone was the National Science Foundation's NSFNet. Along the way, it became known as the "Internet" or simply "the Net." By the 1990s, so many networks had connected and so much traffic was no longer educational that the Internet was on its way to becoming commercial. See ARPAnet.

And It Did in 1995
In 1995, the Internet was turned over to large commercial Internet providers (ISPs), such as MCI, Sprint and UUNET, which took responsibility for the backbones. Regional ISPs linked into these backbones to provide lines for their subscribers, and smaller ISPs hooked into the regional ISPs. Today, AT&T and Verizon are major Tier 1 backbones.

The TCP/IP Protocol
Internet computers use the TCP/IP communications protocol as well as every computer on a local network at home or in the office. An Internet server, no matter its size, is a "host" and always online via TCP/IP, providing email, Web and other services. In the early days, the Internet was connected to non-TCP/IP networks through gateways that converted to and from TCP/IP. See TCP/IP.

Another Internet
Some of the original academic and scientific users of the Internet developed their own Internet once again. Internet2 is a high-speed academic research network that was started in much the same fashion as the original Internet (see Internet2). See Web vs. Internet, IoT, World Wide Web, how to search the Web, intranet, NAP, hot topics and trends, IAB, information superhighway and online service.

The Beginning of the Internet

This four-node network diagram (annotated for this example) was the beginning of the ARPAnet and eventually the Internet. (Image courtesy of The Computer History Museum.)

How the Internet Is Connected

Small Internet service providers (ISPs) hook into regional ISPs, which link into major backbones that traverse the U.S. such as AT&T, Verizon and Xfinity (Comcast). This diagram is conceptual because ISPs often span county and state lines.