In the good old days, data was often moved from system to system (and still is) using a Comma Separated Values (CSV) file, and life was simple. Sometimes the definition of this file becomes blurred as the “C” is CSV (comma) is often replaced by an alternative separator.
You may also get options to use text qualifiers and escape characters, ensuring that if your separator exists in text, then you have a way of ensuring that it is never interpreted as a fields separator.
Things become a little more difficult when you have relationships in in your data, for example, Customers have Orders and Orders have Line Items, meaning that you now have to split your data in to multiple files.
Along comes XML
Amongst other things, XML came along to address this problem. An Extensible Mark-up Language that allows you to clearly define your data, including its types and relationships.
One of the problems with XML is that it is verbose and, sometimes, becomes inappropriately used, complex and poorly defined.
As well as XML, there are other formats that attempt to achive the same goal, such as JSON.
The Extensible Delimiter Separated Values (XDSV) format takes the best aspects of both CSV and XML to provide a file format that support a simple yet effective multi-schema architecture.