What is Web 2.0?

In alluding to the version-numbers that commonly designate software upgrades, the phrase "Web 2.0" hints at an improved form of the World Wide Web. Technologies such as weblogs (blogs), social bookmarking, wikis, podcasts, RSS feeds (and other forms of many-to-many publishing), social software, web application programming interfaces (APIs), and online web services such as eBay and Gmail provide a significant enhancement over read-only websites. Stephen Fry (actor, author, and broadcaster) describes Web 2.0 as "an idea in people’s heads rather than a reality. It’s actually an idea that the reciprocity between the user and the provider is what’s emphasized. In other words, genuine interactivity if you like, simply because people can upload as well as download".[6] The phrase "Web 2.0" can also refer to the transition of websites from isolated information silos to interlinked computing platforms that act like software to the user. Web 2.0 also includes a social element where users generate and distribute content, often with freedom to share and re-use. One perceived result is a rise in the economic value of the Web as users can do more online.
Earlier users of the phrase "Web 2.0" employed it as a synonym for "Semantic Web". The combination of social-networking systems such as FOAF and XFN with the development of tag-based folksonomies, delivered through blogs and wikis, sets up a basis for a semantic web environment.
O'Reilly regards Web 2.0 as business embracing the web as a platform and utilising its strengths (global audiences, for example). O'Reilly considers that Eric Schmidt's abridged slogan, don't fight the Internet, encompasses the essence of Web 2.0 — building applications and services around the unique features of the Internet, as opposed to building applications and expecting the Internet to suit as a platform (effectively "fighting the Internet").

In their (O'Reilly) initial brainstorming, they formulated their sense of Web 2.0 by example:


Web 1.0 --> Web 2.0
DoubleClick --> Google AdSense
Ofoto --> Flickr
Akamai --> BitTorrent
mp3.com --> Napster
Britannica Online --> Wikipedia
personal websites --> blogging
evite --> upcoming.org and EVDB
domain name speculation --> search engine optimization
page views --> cost per click
screen scraping --> web services
publishing --> participation
content management systems --> wikis
directories (taxonomy) --> tagging ("folksonomy")
stickiness --> syndication

sources: wikipedia, O'Reilly website