In 1989, Tim Berners-Lee, a software engineer at CERN, wrote a proposal for a system to link documents across the internet. By 1991 he had built the three pieces that still define the web: the URL (an address for any resource), HTTP (the protocol to fetch it), and HTML (the language to write pages in).
Why it mattered
The internet already existed, but using it took expertise. The Web added a simple, universal way to publish and follow links between documents — and, decisively, Berners-Lee and CERN released it royalty-free. That openness let it spread without permission or licensing, and within a few years it had reshaped commerce, media and daily life. Almost everything you do online rides on those three inventions.