A metadata record consists of a set of attributes, or elements, necessary to describe the resource in question. For example, a metadata system common in libraries -- the library catalog -- contains a set of metadata records with elements that describe a book or other library item: author, title, date of creation or publication, subject coverage, and the call number specifying location of the item on the shelf.

Meta tags are used in the header of web pages to provide information to various applications about the content of the page or the site. The Dublin Core system although not required gives access to information to a broader range of services other than the major search engines. Using the system does not penalise a website in any way and the data is ignored by applications that cannot utilise it.

Thanks Dublincore METADATA Initiative.