You can read about it here and here. Basically, it's a text format to describe data that is easy for both human and computers to understand. It was created to ease the process of exporting and importing data from one system to another.
XML is defined as:
XML is an abbreviation for eXtensible Markup Language. It is a markup language similar to HTML, but there are some differences. ML is not a programming language that you can 'run' or 'execute'. This does not do anything. It is only a way of defining, transmitting, validating, and interpreting data.See original page: http://www.functional-marketing.com/xml-definition.html#ixzz1cViDMUH6 Under Creative Commons License: Attribution
Other people asked questions on similar topics, check out the answers they received:
Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them