What is the difference between HTML and XML?

Answer 1

HTML is used to create basic structure for a webpage. The browser parse the HTML text and create User interface with that following W3C standard. Since HTML tags are fixed in standard, you can't create new tags in general (it's possible now with HTML5).
XML is generally used to store text data only. Text data is easy to arrange in XML, which can later be sent as a response from Webserver to the requesting webpage or app.

Answer 2

That html is not "eXtensible". Apart from that, they're often used for different reasons. There are some other differences, for example, the fact that html code has default styling applied to certain tags.

Answer 3

The Extensible Markup Language is a generic markup metalanguage that derives from SGML. This syntax is called "extensible" because it allows to define different namespaces, that is, languages ​​with each their vocabulary and grammar, such as XHTML, XSLT, RSS, SVG ... It is recognizable by its use of Rafters (<,>) framing the tags.