The World Wide Web (abbreviated as WWW or W3, commonly known as the web) is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia and navigate between them via hyperlinks.

Tim Berners-Lee, a British computer scientist and at that time employee of CERN, a European research organisation near Geneva, wrote a proposal in March 1989 for what would eventually become the World Wide Web. The 1989 proposal was meant for a more effective CERN communication system but Berners-Lee eventually realised the concept could be implemented throughout the world.

Berners-Lee and Flemish computer scientist Robert Cailliau proposed in 1990 to use hypertext "to link and access information of various kinds as a web of nodes in which the user can browse at will", and Berners-Lee finished the first website in December that year. Berners-Lee posted the project on the alt.hypertext newsgroup on 7 August 1991.

Source: Wikipedia.