"The Extensible Markup Language (XML) is a simple text-based format for representing structured information: documents, data, configuration, books, transactions, invoices, and much more. It was derived from an older standard format called SGML (ISO 8879), in order to be more suitable for Web use."

Source: W3C. XML Essentials. 
Online: https://www.w3.org/standards/xml/core#:~:text=What%20is%20XML%3F,more%20suitable%20for%20Web%20use.