While I looked at several, the best definition I came up with was:

Web 2.0 - A term often applied to a perceived ongoing transition of the World Wide Web from a collection of websites to a full-fledged computing platform serving web applications to end users. It refers to a supposed second-generation of Internet-based services—such as social networking sites, wikis, communication tools, and folksonomies—that emphasize online collaboration and sharing among users.

Hope that helps.

Thanks hogback,

I still have to try to understand what this is.I am a 48 soon to be 49yr old male that is VERY I.T. challenged

Web 2.0 is basically the change from having all websites be fairly static, you the user can't interact with them, makes suggestions, interact with other's that might be coming to that site. My understanding is that it is the fact that blogs have pretty much taken over much of the internet. Many people, particularly those genius 20-30 something out there that were born with a keyboard in their crib are not even building what we would traditionally think of as a website but building websites on blog platforms. www.wordpress.org

Probably has the larger percent of the market share.

The social networking part of it comes in with facebook, twitter, digg, stumble upon, where internet folks can share their experiences, knowledge, favorite websites, blog entries and personal life if they want through the sites noted above. For instance if I update the "what I'm doing" on my facebook profile, that goes into my friendfeed, my twitter, plaxo, linked in and any other of my social networks that I've hooked up together.

To really understand it you sort of have to just jump in and get started.. friend people that have similar interests to you, much like you are doing here at TBD.

TBD itself is a 2.0 web set up.

Hope that helps.

:)