What is the difference between HTML and XHTML?

Ans: Html is a hypertext markup language where XHTML is extensible hypertext markup language. Both languages are used to create web pages. XHTML is XML based while HTML is SGML based. Compare to HTML XHTML is strict and does not allow the users to get away with the lapses in coding and structures. 

12File extensions of HTML:  .html, .htmFile extensions of XHTML: .xhtml, .xht, .xml, .html, .htm.