Um, AFAIK, there was no web 1.0. It just represents the time of the internet before web 2.0 became reality (as mentioned above, mainly static general web sites, etc).
Web 2.0 is currently the "standard" web tech dominating web applications - basically it refers to social networking, ie: as mentioned above, facebook, youtube, etc.
Web 3.0 is the next gen of typical web applications - there are rumours as to exactly what it entails, but the last I heard they are planning the whole remote appliance technology. In our words, providing an interface for your stove, fridge, bathtube, etc through the net. So you'll be able to connect remotely to your home. While this whole thing will still need to evolve, the basic principle is already in use.
In essence, the difference between the web versions is the web applications that are predominant. The technology used for developing and implementing the applications also changes, and this change is included in the whole shift between the different versions.