Here's the article about Web 2.0 on Wikipedia:  http://en.wikipedia.org/wiki/Web2.0

Here's a 2.0 site that has many examples of other Web 2.0 sites:  http://www.killerstartups.com

In a nutshell 2.0 is what you get when anyone on the planet can create a virtual product or service.  It occurs when an entrepreneur leverages the Internet to create a central meeting place for a given type of service.

Take YouTube as an example.  They've created a place where people can upload and view videos over the Internet.  The uploaders want their video seen, the viewers want some quick entertainment.  YouTube, the company, sits in the middle tracking popularity, ratings, and users' comments.  That's Web 2.0.  YouTube didn't really create anything new.  All it did was provide a medium that allowed people to connect to each other in a new way, and for a centralized purpose:  sharing video clips.

The "old" way would have you paying for access to a video clip.  The 2.0 way is all about the value added by the network.  What can you do with the knowledge that the History of Dance guy and the treadmill musicians are worth millions of hits per day?  You could put up a password system and charge admission for premium content.  But you'd make more money by giving it away.  Leverage the network.  Put up a "send to a friend" email link and raise your advertising rates for ads that appear with popular videos.  Everyone wins.

Why should you care about any of this?  For one thing it represents a complete shift in the way that things have traditionally been done.  Scarcity economics is our current business model.  That means, I have a product or service that you need so I'm going to make you pay for it.  I can expect that you will pay for it, because you can't get this product or service anywhere else.

Now imagine a world where you can't make any money selling something that can be delivered digitally.  (Well, you'll always have to buy physical things, at least until personal fabricators mature...)  All electronic data and media that can be converted to electronic data is free.  Now imagine if all profits were based on a company's ability to leverage network popularity and usefulness to the community.  This is also something we're experiencing right now.

Even if you pay for something, like the Vista operating system, is it worth the investment without the backing of the community?  Part of what you paid for is technical support, but technical support is useless if they can't fix your problem.  The company's tech support may not be able to help you if they haven't encountered the problem before.  They wouldn't have encountered the problem before if fewer people are using the OS. 

Is the investment worth it if your hardware and software isn't compatible with Vista?  That's another aspect of the value added by a community. 

Let's say you download a cracked version of Vista for free.  Tech support still doesn't solve your problems and answers aren't available online.  (Assuming that no one else has encountered the issue you're having, fixed it, and written about it.)  It's also not compatible with your hardware and software.  Now, is the amount of time you spent downloading and the cost of the blank DVD worth it?  Probably not.

Imagine this scenario.  Your current computer dies.  You need a new one.  You head over to wherever you buy computers and get one with Vista preinstalled.  (At this point, you don't have much of a choice.)  You get the computer home, hook it up, and your printer doesn't work.  Neither does your scanner.  You call a tech.  He charges you for troubleshooting then declares there's nothing he can do.  There are no drivers for Vista for your hardware.  You can wait a few months and hope for an update or you can go buy different hardware.  The same thing goes for your software.  Some of it won't even install.  Time to buy more new stuff.

(This is the reason most people suggest waiting for the first service pack release before upgrading to any new version of Windows.  The first service pack signifies that the community has caught up with the software.  Most of the initial bugs will have been detected and corrected by then.  Most of the hardware and software that is going to be updated will have been updated by this time.)

Contrast that situation with what you see in the Linux community.  You download the software for free.  Most of your hardware already works because the community offers free driver development.  When you have a problem you can connect with others having the same issue.  When you want to learn how to do something, the community is there to help with tutorials, videos, and articles.  Because Linux is open source, software development and improvement occurs much faster than a traditional closed source system.  As an end-user this means that problems and difficulties you experience today won't be a factor in a month or two. 

What if a month or two won't work for you?  What if you can't understand the geek speak in the forums or the tutorials?  If you find yourself at that point, now you can pay for something.  You can pay for and get support from your Linux distro of choice.  You can pay a tech to find, read, and perform whatever steps are necessary to get your computer working the way you want.  You can even hire someone to write software to fix whatever problem you're having. 

The moral of the story is that the community adds value.  The ability to connect with anyone, anywhere, creates that community.  The next time you're looking for a product or a service, look beyond what the company itself offers and research the community behind it.