The Semantic Web is a mesh of information linked up in such a way as to be easily processable by machines, on a global scale. You can think of it as being an efficient way of representing data on the World Wide Web, or as a globally linked database. (http://infomesh.net/2001/swintro/)
Tim Burners-Lee, the person who came up with WWW, HTTP, HTML and URl's also invented the Semantic Web. The Semantic Web is used to represent data and information from any website to interpret anything it reads on the web. It allows programs and machines to be able to translate the information on a website just by "reading". The Semantic Web is said to be an extension of the Web that facilitates the interaction between the programs and people. The Semantic Web can can be said to represent data about data in the WWW.
