eXtensible Markup Language - a markup language for storing and transporting structured data. Like HTML but designed for data instead of web pages.
Bank systems often exchange transaction data using XML format because it's both human-readable and machine-readable.
XML is an open data format/markup language, not a cloud provider service. All major clouds support storing, validating, transforming, and exchanging XML using their compute, integration, and storage services (for example, APIs, message queues, ETL, and object storage).