/hiːt mæp/

Heat map is a data visualization technique that displays visual cues in different colors. 

Heat map is used to portray how visitors interact with a webpage. Red color signifies that a certain area has more interactions than, for example, a blue area that has less interactions. 

Heat map is useful as the data it shows on users' interactions with the main elements such as buttons, CTAs, links, opti-ins allows for webpage improvements based on users’ experience (or the lack of) with it.