Originally Posted by StuartD

There's a good explanation here: http://en.wikipedia.org/wiki/Web_2
as it entails a bunch of different things.

But the primary aspects are that it's developed primarily without tables, using CSS instead.... and should encorporate some kind of AJAX/DHTML or other "new" old technology....
and that it has to be community driven, much like youtube gets videos from users, wiki gets entries from users, myspace grows by user filled pages, etc.