You are invited to read the excellent
http://www.oreillynet.com/pub/a/oreilly/tim/news/2005/09/30/what-is-web-20.html discussion.
http://en.wikipedia.org/wiki/Web_2.0
The retroactively-labeled "Web 1.0" often consisted of static HTML pages, rarely (if ever) updated. They depended solely on HTML, which a new Internet content-provider could learn fairly easily. The success of the dot-com era depended on a more dynamic Web (sometimes labeled Web 1.5) where content-management systems served dynamic HTML web-pages generated on-the-fly from a content database more amenable than raw HTML-code to change. In both senses, marketeers regarded so-called "eyeballing" as intrinsic to the Web experience, thus making page-hits and visual aesthetics important factors.
About comparing web2-web1 : 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