HTML, XML, HTM, MHT whether they are the same or different, and if different, what is the difference?

Answer 1

Gavrie Sashenka even XML younger, it's still useless if I compare it with JSON

Answer 2

XML: have an infinite number of possible elements, and XML document can't be a HTML document, XML have to be well formed and valid before they can be printed,XML is younger than HTML.
HTML has a very strict set of predefined element,a HTML document can be a XML document,HTML document meaning or browse instruction by their use,HTML is older than XML
https://www.sololearn.com/discuss/1130693/?ref=app
https://www.sololearn.com/discuss/1369370/?ref=app
https://www.sololearn.com/discuss/804284/?ref=app

Answer 3

Thank you very much