Today it means: Usually preceded by the: all of the hypertext documents (web pages) on the Internet collectively, which are (1) stored in various inter-hyperlinked computers around the world, and (2) retrieved typically by means of the Hypertext Transfer Protocol (HTTP) or (currently more often) its secure version (HTTPS), among others. Full definition →
From worldwide + web. Coined by English computer scientist Tim Berners-Lee and Belgian engineer and computer scientist Robert Cailliau in a paper published on 12 November 1990 (see quotations below).
Etymology from Wiktionary, CC BY-SA 4.0.