Microformat
World Wide Web-based approach to semantic markup which uses HTML/XHTML tags supported for other purposes to convey additional metadata and other attributes in web pages and other contexts that support (X)HTML, such as RSS / From Wikipedia, the free encyclopedia
A Microformat is an attempt to re-use existing content in HTML and XML documents. Such content may be information on how to contact someone, or it may be geographical coordinates, for example. This information can then be processed by software more easily.
Technically, this kind of information is already there. A microformat aims at making this information accessible more easily. That way, tags might be added to flag the information.