HTML is not a programming language, it is a markup language,A markup language is a set of markup tags,HTML uses markup tags to describe web pages this are some description about html.and XHTML. XHTML is a stricter and cleaner version of HTM, it is HTML defined as an XML application, this are those what I all just remember about our lesson.
In other topics we also discussed about tags. first of all what a tag is ? It is a keyword surrounded by angle brackets like <html> its normally come in pair like <hmtl> & </hmtl>. The most important thing that cannot be forget to put when creating a simple web page is the tag <html> if this is forgotten to insert your web page will not open or some errors may occure.
But when creating a complicated web page you must put a <!doctype> at the beginning of your html. It is use for the web page to appear in any kind of browser you want like google chrome,internet explorer and many more, you must not forget to close all tags you make,