Definition of WWW is:
a system of Internet servers that support specially formatted documents. The documents are formatted in a language called HTML (HyperText Markup Language) that supports links to other documents, as well as graphics, audio, and video files. This means you can jump from one document to another simply by clicking on hot spots. Not all Internet servers are part of the World Wide Web.
VoIP has nothing to do with the web, it's an independent Internet Protocol and can work without the web.
And web2 is just a buzz word to describe advances in Client side technology that makes browser based applications more complex and behave like traditional desktop apps, when the web was originally envisioned all this "web2.0" stuff was part of that vision.
Web 2.0 just a buzz word. Period.