HTML is HyperText Markup language XHTML is Extensible HyperText Markup Language XML is Extensible Markup Language
HTML is used to create structured documents It serves the same function as HTML but with the same rules as XML documents XML provides rules for creating, structuring, and encoding documents.
Filename extensions are .html or htm. Filenames extensions are .xhtml, .xht, .xml. Filenames extensions are .xml.
Various versions of HTML are HTML2, HTML3.2, HTML4.0 and HTML5. Various Versions of XHTML are XHTML1,XHTML1.1, XHTML2, XHTML5. Various Versions of XML are XML1.0

NOTE: This front end developer interview questions is the most commonly asked. Make sure to study in detail this.

BY Best Interview Question ON 17 Jan 2021