The Semantic Web is a mesh of data associated in such a way they can easily be processed by machines instead of human operators. It can be conceived as an extended version of the existing World Wide Web (WWW), and it represents an effective means of data representation in the form of a globally linked database. By supporting the inclusion of semantic content in Web pages, the Semantic Web targets the conversion of the presently available Web of unstructured documents to a Web of information/data.
Source: Semantic Web