A heat map (or heatmap) is a graphical representation of data where values are depicted by color. Heat maps make it easy to visualize complex data and understand it at a glance.
The practice we now call heat maps is thought to have originated in the 19th century, where manual gray-scale shading was used to depict data patterns in matrices and tables.
Heat maps also usually display the average fold, which is the portion of the page people see on their screen without scrolling as soon as they land on it.