A markup language is a modern system for annotation that presents text with positioning and formatting. It is used in many cases by browsers as a presentation language
Markups are used as document formats within the World Wide Web.
The idea and terminology evolved from the "marking up" of manuscripts
<ul><li>revision instructions by editors, traditionally written with a blue pencil on manuscripts.
Markup instructs the software displaying the text to carry out appropriate actions, but is omitted from the version of the text that is displayed to users.
Examples:
typesetting instructions such as those found in troff, TeX and LaTeX, or structural markers such as XML tags.
widely used markup language: HyperText Markup Language (HTML)
HTML, which is an instance of SGML (though, strictly, it does not comply with all the rules of SGML), follows many of the markup conventions used in the publishing industry in the communication of printed work between authors, editors, and printers.