In simple terms, semantic web denotes usage of XHLML for content and of CSS for presentation. The semantic web is a developing extension of the World Wide Web in which web content can be articulated not only in natural language, but also in a format that can be read and used by software agents, thus permitting them to find, share and integrate information more easily.

Advantages
The semantic web provides a general framework that allows data to be shared and reused across application, enterprise, and community boundaries. It is a mutual effort led by W3C with participation from a large number of researchers and partners. It is based on the Resource Description Framework (RDF). It enables end-user to find documents and contextually relevant information. Semantic applications exploit metadata and on the way with associated knowledgebase. In Semantic Web, documents are marked up with semantic metadata.

Uses
The semantic web is a dream of information that is understandable by computers, so that they can perform more of the tedious works involved in finding, sharing and combining information on the web.

For more information please visit http://www.w3c.org