XML Extensible Markup Language, or XML for short, is a new technology for web applications that lets you create your own tags. Structured information contains both content and some indication of what role that content plays. XML provides a mechanism to impose constraints on the storage layout and logical structure of the document. XML documents are made up of storage units called entities, which contain either parsed or unparsed data. Parsed data is made up of characters, some of which form character data, and some of which form markup.
Markup encodes a description of the document's storage layout and logical structure.
XML provides a mechanism to impose constraints on the storage layout and logical structure. A software module called an XML processor is used to read XML documents and provide access to their content and structure. It is assumed that an XML processor is doing its work on behalf of another module, called the application.