What is CSV?

The least glamorous and most durable data format there is: rows of values separated by commas, readable by every spreadsheet and database ever written. All its subtlety is in quoting - a value with a comma in it has to be wrapped in quotes, and a quote inside that has to be doubled.

What is XML?

Verbose, strict, and still holding up enormous amounts of the world - government feeds, financial messaging, publishing, office documents. JSON took the web from it, but anywhere with schemas and validators and twenty years of history, XML is what's on the wire.