What is xml and XHTML

Answer 1

XHTML is an adaption of classic HTML to XML standard. Classic HTML uses the SGML standard. XML is a general markup language standard for structuring data in text files.

Answer 2

HTML is the HyperText Markup Language, which is designed to create structured documents and provide for semantic meaning behind the documents.
HTML5 is the next version of the HTML specification.
XML is the Extensible Markup Language, which provides rules for creating, structuring, and encoding documents. You often see XML being used to store data and to allow for communication between applications. It's programming language-agnostic - all of the major programming languages provide mechanisms for reading and writing XML documents, either as part of the core or in external libraries.
XHTML is an XML-based HTML. It serves the same function as HTML, but with the same rules as XML documents. These rules deal with the structure of the markup.
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XHTML is the fifth version of HTML
HTML5 is the sixth version of HTML
HTML5 & XHTML are used to build websites pages
XML is used to store data
XHTML is like HTML or HTML5 but with XML rules ☺

Answer 3

XML is the syntax, the opening tag must be paired with a closed tag.
XHTML is to follow XML syntax strictly. For example, you should use <br/> and <img/> instead of <br> and <img>, self-closing for single tags