What is Web 2.0?

What is web 2.0? There are lots of definitions:

From WikipediaWeb 2.0, a phrase coined by O'Reilly Media in 2003[1] and popularized by the first Web 2.0 conference in 2004[2] , refers to a perceived second generation of web-based communities and hosted services — such as social-networking sites, wikis and folksonomies — which facilitate collaboration and sharing between usersweb20.jpg

IN OTHER WORDS....
Web 1.0

Web 2.0
DoubleClick
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Google AdSense
Ofoto
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Flickr
Akamai
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BitTorrent
mp3.com
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Napster
Britannica Online
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Wikipedia
personal websites
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blogging
evite
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upcoming.org and EVDB
domain name speculation
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search engine optimization
page views
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cost per click
screen scraping
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web services
publishing
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participation
content management systems
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wikis
directories (taxonomy)
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tagging ("folksonomy")
stickiness
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syndication

Web 2.0 by example: O'Reilley Media Article
Check out this great Web 2.0 Video on YouTube
Web 2.0 icons - Click the purple arrow in the bottom left corner to advance
2007 Web 2.0 Awards - listed by category.