What are social bookmarking websites?
The basic principle behind social bookmarking websites is to be able to have your own favourites section that is accessible from anywhere in the world. Furthermore, such online based services integrate the social component that allows interactions between individuals with the ability to view each others bookmarks. The various platforms available have their own individual add ons, such as category based browsing, rating the bookmarks, community commenting etc.
The key is the social component of managing and browsing content. Virtually, someone else, who you might even know, has found this content relevant. Often enough some sort of statistical information is kept regarding how many people have accessed the piece of content or bookmark with ability to comment and further share the relevant information, spreading it throughout the Social Web.