A markup is a distinction, highlighting, or marking. Markups are sequences of symbols and characters that are inserted at specific locations in a document.
Markups can be used to describe the form of presentation, printing or structure of documents. To better structure documents, for example, by using subheadings, degrees of boldness or underlining. They can also be comments, separators and processing instructions.
Markups can be used to define the layout of word processing programs, and to format text and data in e-mails and database programs. The individual markup elements separated from each other are called tags.