XML documents, like HTML documents, contain text and can be written using any text editor or word processor, such as Microsoft Notepad. For ease of reference, XML documents normally are saved with the .xml extension. The .xml extension ensures that the document is easily recognized as containing XML and that applications, such as Microsoft Internet Explorer, view the document as such.
XML documents are built using text content marked up with tags. For a document describing items in an inventory, these tags could be
<item_description>. In addition to tags, XML documents can contain other types of markup, including attributes, processing instructions, entity references, comments, ...