WorldWideWeb is a service which allows going back and forth between different documents (websites). To do so, a web-browser which picks up the information from a web-server is necessary.
WWW is mainly based on the standards HTTP, HTML and URL.
HTTP is the protocol which allows a web-server to download information from a specific server.
URL is the explicit address of a document. They are used in hyperlinks enabling logical interconnections.
In common language WWW is often equated with internet, which is not correct, since WWW is just one of many possibilities of using the internet (others would be e-mail, FTP or chat).
WWW was developed in 1989 by Tim Berners-Lee at CERN in Switzerland. It was basically designed for exchanging results of the latest research with colleagues more easily.
After the publication of the graphical browser Mosaic by Marc Andreessen in 1993, WWW became available for the broad public and started its incomparable triumph.