Standard text-encoding system consisting of a set of symbols inserted in a text document to control its structure, formatting, or the relationship among its parts.
The most widely used markup languages are SGML , HTML , and XML . The markup symbols can be interpreted by a device (computer, printer, browser, etc.) to control how a document should look when printed or displayed on a monitor. A marked-up document thus contains two types of text: text to be displayed and markup language on how to display it.