What is XML?
Extensible Markup Language, or ''XML,'' is an open standard base that allows agencies to exchange data, regardless of computer system or platform. XML defines the structure and meaning of data records through simple but carefully defined syntax rules and provides the common framework to facilitate cross-platform data exchange.
With XML, existing systems can remain in place, and the data is translated as it enters and exits each system without changing the meaning of the data or how it appears in the originating system.
XML is designed to transmit both data and the meaning of the data. It accomplishes this by being a markup language, a mechanism that identifies different structures within a document. Structured information contains both content (such as words, pictures, or video) and an indication of what role content plays, or its meaning. XML identifies different structures by assigning data "tags" to define both the name of a data element and the format of the data within that element. Elements are combined to form objects.
XML Tutorial: http://www.w3schools.com/XML/default.asp