TL;DR
A heatmap of a website is a color-coded data visualization tool. It helps website owners and companies understand how their visitors interact with different areas of their websites, i.e. where the “hotspots” or “coldspots” of the website are located. Data visualization is done in real-time. On the basis of this information, you can then further optimize your website and increase your conversion rate, knowing that, for example, important content or actions are not reached or seen by your visitors, as they are in a “cold area".
How heatmaps work
Heatmaps use colors to visualize the intensity of visitor interaction on different sections of the pages of your website.
A color scheme from warm to cold is used to display this interaction data: