Explain what is HTML language with an example?

HTML is the HyperText Markup Language.
HTML files are text files featuring semantically tagged elements.
HTML filenames are suffixed along with .htm or .html.
Here's a simple HTML file:

A level one heading

Hello there. This is very important.

Names enclosed in angle brackets such as , , and are end-tags. The text in among , My First HTML Document in the above example, is the title of the page.

As you can see from the above example elements may, in general, nest. However they may not overlap (though some browsers can handle this).