Sometimes referred to as a “network of networks,” the Internet is generally defined as a global network connecting millions of computers. The Internet is a global wide area network that connects computer systems across the world.
No one actually owns the Internet, and no single person or organization controls the Internet entirely. The Internet is more of a concept than an actual tangible entity, and it relies on a physical infrastructure that connects networks to other networks. This physical infrastructure is what we call the world wide mesh of telecom towers, OFC lines, switches, routers, gateways etc.
The first host-to-host network connection named ARPANET was built on October 29, 1969 by the Advanced Research Projects Agency (ARPA) of the U.S. Department of Defense.
The technology continued to grow in the 1970s after scientists Robert Kahn and Vinton Cerf developed Transmission Control Protocol and Internet Protocol (TCP/IP) that described how data could be transmitted between multiple networks. ARPANET adopted TCP/IP on January 1, 1983 and the more recognizable form of Internet came up in 1990 when computer scientist Tim Berners-Lee invented the World Wide Web (WWW).
NOTE: Internet and WWW are not synonymous. These are technically two different things.