XML (Extensible Markup Language) is a markup language used to structure, store and transmit data in a machine-readable format. It is similar to HTML, which is used to structure and format data for display in a web browser, but it is more flexible and extensible and not intended for display.

XML uses tags to define the structure of a document and to identify specific data. These tags are defined by the person or organisation creating the XML document and can be adapted to the needs of the particular application.

XML is often used to transfer data between different systems or to store data in a format that can be easily retrieved and processed by computers. It is also used to create documents that can be shared between different applications or platforms, as it provides a standardised way to structure and organise data.