HTML is not a computer language such as C++ or Pascal.

It's just a system for describing documents.

A WWW browser interprets the HTML code and displays it.

HTML is a special version of SGML (used by big companies for exchange of data) focused on Hypertext.

HTML code is written in ASCII format. This is a big advantage, because ASCII can be read by almost any platform ("IBM", Mac, UNIX,...) thus making the WWW usable for any platform as long as viewer programs, the browsers, exist.