What is HTML?
HTML is a sub-language of SGML, or Standard Generalized Markup Language.
SGML is a system that defines and standardizes the structure of documents.
Both SGML and HTML utilize descriptive markup to define the structure of an area of text. In general terms, descriptive markup does not specify a particular font or point size for an area of text. Instead, it describes an area of text as a heading or a caption, for example.
Therefore, in HTML, text is marked as a heading, subheading, numbered list, bold,
italic, etc.