Sometimes it’s just better to say- here is where someone got it all together- and tell you to click over and read their post.
This is one of them- the presentations on this site will help make it clear to you, enjoy:

Web 1.0 – That Geocities & Hotmail era was all about read-only content and static HTML websites. People preferred navigating the web through link directories of Yahoo! and dmoz.

Web 2.0 – This is about user-generated content and the read-write web. People are consuming as well as contributing information through blogs or sites like Flickr, YouTube, Digg, etc. The line dividing a consumer and content publisher is increasingly getting blurred in the Web 2.0 era.

Web 3.0 – This will be about semantic web (or the meaning of data), personalization (e.g. iGoogle), intelligent search and behavioral advertising among other things.

via What is Web 3.0? Semantic Web & other Web 3.0 Concepts Explained in Plain English.