Difference Between Html and Xhtml

HTML (Hyper Text Markup Language) :- is the main markup language for creating web pages and
other information that can be displayed in a web browser. HTML is written in the form of HTML elements consisting of tags enclosed in angle brackets , within the web page content. The purpose of a web browser is to read HTML documents and compose them into visible or audible web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page.

XHTML (Extensible HyperText Markup Language) :- is a family of XML markup languages that mirror or extend versions of the widely used Hypertext Markup Language (HTML), the language in which web pages are written. While HTML (prior to HTML5) was defined as an application of Standard Generalized Markup Language (SGML), a very flexible markup language framework, XHTML is an application of XML, a more restrictive subset of SGML. Because XHTML documents need to be well-formed, they can be parsed using standard XML parsers—unlike HTML, which requires a lenient HTML-specific parser.
Difference between HTML and XHTML :- 
XHTML is not so much different from HTML 4.01 standard. The major differences are:

• 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.