What is HTML?

Hypertext Markup Language (HTML) is based on SGML Standard Generalized Markup Language (SGML), a universal system for document style sheets. SGML specifies tags for each part of a document, such as a heading or a sub-heading, so that it can be displayed by any SGML-aware word processor. SGML also allows hypertext links between parts of a document and between documents.

HTML is a subset of SGML, obeying all SGML rules and conventions. HTML tags are used to mark up the hypertext documents sent by a Web server at the request of a browser. The browser then reads the tags, and parses (translates) them into suggestions on how your computer should display the document, or where to go if a link is clicked. The tags don't control exactly how a Web page is displayed -- this is left up to each individual browser. There are good reasons for this:

not all users have the same fonts installed on their computer, and

the text has to be displayed on all sizes of monitor.