What is HTML?

The web's document format, and incidentally a place an enormous amount of tabular data ends up - published tables that were never offered as a download. Pulling those out is usually easier than asking whoever published them for the numbers.

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.