From Social Patterns
Social Bookmarking is a way for a community of users to collectively organize hyperlinks to web-based knowledge resources in a community-managed list. Social bookmarking uses keywords and metadata to organize these resources instead of utilizing a conventional hierarchical folder organization. Retrieval of these information from such systems is based on keyword search.
Social bookmarking is thus a form of One-Time Sharing for gathering pointers, generally in the form title, link, description (the same canonical form used for early blogging and RSS).
Social bookmarking thrives via the convenience of a Bookmarklet, which moves the action of bookmarking socially into the same part of the interface (the "browser chrome") where mark one solipsistic bookmarking was always done.
Whether invoked via Bookmarklet or Share This widget the social bookmarking interface can guide the person posting the pointer toward capturing and reviewing the title and description metadata for the bookmark.