Heatmaps provide visual representation of user interactions with a webpage, using color codes. The color scale ranges from blue (not popular) to red (very popular).

Heatmaps allow you to quickly assess which website elements users click on, ignore, scroll thorough and more.

Here is an example of a heat map based on cursor movement:

Here is the information about heat map feature in Piwik PRO:
Smartlook integration session recordings heatmaps