A Markup Language is a computer language in which data and instructions describing the structure and formatting of the data are embedded in the same file. The term derives from the way e.g. an editor or a printer would "mark up" a text, with annotations in the body and margins of the document.
It could be said that the mother of all markup languages was SGML: Standard Generalized Markup Language. This was developed at IBM during the 1970s and 1980s, and eventually became an ISO standard. Several types of markup used commonly derived from the ideas in SGML, including HyperText Markup Language (HTML) and eXtensible Markup Language (XML). Some other types of markup languages developed independently, such as TeX and LaTeX.