Social bookmarking is a method for Internet users to organize, store, manage and search for bookmarked resources online. Unlike file sharing, the resources themselves aren't shared, merely bookmarks that reference them.
In a social bookmarking system, users save links to web pages that they want to remember and/or share. These bookmarks are usually public, and can be saved privately, with specified people or groups, or other combinations of public and private domains. The allowed people can usually view these bookmarks chronologically, by category or tags, or via a search engine.
There are hundreds of social bookmarking sites available in the U.S. If you’re including the rest of the world, that number more than quadruples.