An XML file is a file format used to store and transport data in a structured way. It is a markup language that defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. XML files contain tags that define how the document should be structured and how it should be stored and transported over the internet. These tags indicate the type of element and allow computer programs to easily structure and fetch the data that they need. XML files can be opened and edited with text editors, web browsers, online editors, and application-specific programs. Some popular file formats, such as Microsoft Office files, are built with XML. XML also provides the base language for communication protocols such as SOAP and XMPP.

In summary, an XML file is a file format used to store and transport data in a structured way. It contains tags that define how the document should be structured and how it should be stored and transported over the internet. XML files allow computer programs to easily structure and fetch the data that they need.