A markup language is a set of words and symbols for describing the identity of pieces of a document (for example ‘this is a paragraph’, ‘this is a HEADING’, ‘this is a list’, ‘this is the caption of this figure’, ETC). Programs can use this with a STYLE sheet to CREATE output for screen, print, audio, video, Braille, etc.
Some markup LANGUAGES (e.g. those used in word processors) only describe appearances (‘this is italics’, ‘this is bold’), but this method can only be used for display, and is not normally re-usable for anything else.

A markup language is a set of words and symbols for describing the identity of pieces of a document (for example ‘this is a paragraph’, ‘this is a heading’, ‘this is a list’, ‘this is the caption of this figure’, etc). Programs can use this with a style sheet to create output for screen, print, audio, video, Braille, etc.
Some markup languages (e.g. those used in word processors) only describe appearances (‘this is italics’, ‘this is bold’), but this method can only be used for display, and is not normally re-usable for anything else.