XML is an abbreviation for Extensible Markup Language, a type of computer programming language. It is a standard and specification designed to transport and store data.W3Schools.com: Introduction to XML Users can create custom data elements and markup languages. XML is designed to easily transfer these elements between users, primarily over the Internet.
Different From HTML
Because it is text-based and built upon programming elements called tags, XML is often compared to HTML. But the two languages are fundamentally different. XML is designed to store and exchange data, while HTML is made for graphically displaying data.W3Schools.com: Introduction to XML