Social bookmarking is a method for Internet users to share, organize, search, and manage bookmarks of web resources. Unlike file sharing, the resources themselves aren’t shared, merely bookmarks that reference them.

Digg is a social news website made for people to discover and share content from anywhere on the Internet, by submitting links and stories, and voting and commenting on submitted links and stories. Voting stories up and down is the site’s cornerstone function, respectively called digging and burying. Many stories get submitted every day, but only the most Dugg stories appear on the front page. Digg’s popularity has prompted the creation of other social networking sites with story submission and voting systems.

From Wikipedia