what is the difference between html and xhtml?

ok this is that i know -XHTML elements must be properly nested. -XHTML elements must always be closed. -XHTML elements must be in lowercase. -XHTML documents must have one root element. basically, XHTML is HTML (all the html tags are found in XHTML) that follows the rules of XML (because it is a family of XML). plz dont forget to vote positively on my answer ^^! good look :)