RDF is a general framework for describing website metadata, or “information about the information” on the website. It provides interoperability between applications that exchange machine-understandable information on the Web. RDF details information such as a site’s sitemap, the dates of when updates were made, keywords that search engineslook for and the Web page’s intellectual property rights.
Developed under the guidance of the World Wide Web Consortium, RDF was designed to allow developers to build search engines that rely on the metadata and to allow Internet users to share Web site information more readily. RDF relies on XMLas an interchange syntax, creating an ontology system for the exchange of information on the Web.
See also “What Is The Semantic Web?” in the Did Yoy Know…? section of Webopedia.