The term "Web 2.0" gets bandied around a lot these days. It refers to things like blogs and wikis… For a fuller definition, this article on oreillynet.com explains What is web 2.0?
But Web 2.0 isn't in fact so cool any longer, as we now have Web 3.0 as well. PC Mag explains What is web 3.0?
To me, evolution of the web order can be defined in single sentences:
1.0 the pushed, one way only web
2.0 the two-way shared web
3.0 the real time collaborative web (3D, isometric or just 2D)
3D is probably actually a better term for it. 3D might well be what the web becomes; 3.0 looks like a clever-clever way of saying "I'm even more up-to-the-minute than all those people (still) talking about Web 2.0".
Even when we get to Web 4.0, however, or Web 14.0 for that matter, don't forget that to you as the teacher what's important is not the technology, but the learning.