Meaning – The term markup, refers to the identification of the components of a document to enable each component to be appropriately formatted, displayed, or used.
The work markup may be simplified to mean edit or add some modifications to the document. Usually, when you receive a document or prepare a document, there may be some terms or sections that may not be very clear on the get-go. In such cases, the creator creates some off-hand notes using a stylus or a text box, to make the content easy to understand.
Example of usage – “Since the location of the party was relatively new, he took a screenshot of the GPS location of the place to visit and created a markup to show the attendees the exact location and any other information.”