Files with the extension “.xml” are known as XML files. XML stands for eXtensible Markup Language and was first conceived by the World Wide Web Consortium, or W3C, in 1996. XML is a subset of the SGML language, which was used to publish technical information. An XML file typically stores data for a website and is written in a language very similar to HTML. However, an XML file has a more rigid structure and stricter rules. An XML file can also be used to share a set of data between two or more software programs. There are several languages based on XML such as XSLT, which is used to add visual styling to an XML file on the Internet, and XQuery, which is used retrieve data from an XML file similar to the way that a query is used to retrieve data from a database.
You can open XML files with a plain-text editor or with a more complex editor such as Open Office, which is free for anyone to download from the Internet. Open Office is an open source productivity suite first released in 2000 that is primarily supported by Oracle. It is available in dozens of different languages.