What is the full form of XHTML ?

XHTML – Extensible HyperText Markup Language

XHTML is a new language, which is designed to work with XML and replace the old Markup Language HTML. We can say that, Extensible HyperText Markup Language combines the flexibility of HTML with the extensibility of XML and increase interoperability with other data formats. It is in many respect similar to HTML with some major changes.

Like With Extensible HyperText Markup Language , you must always put in the end tag :
< p> ..... some text </p>
<p> ..... some more text </p>

XHTML family document types are XML based, and ultimately are designed to work in conjunction with XML-based user agents. Extensible HyperText Markup Language is an official standard of the World Wide Web Consortium (W3C), so it will be compatible to almost all browsers and will be rendered more accurately.