What is JSON?

The format the web runs on. Nested objects and arrays, real types, and a syntax small enough to fit on a postcard. It maps badly onto a grid, which is why converting deeply nested JSON to a spreadsheet always involves losing something.

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.