Heat map allows you to analyse your shooting group pattern composed from shots over longer period of time.
Using a large number of shots it is possible to estimate the probability of hitting a given point on the target and visualise the shape of your shot fall.
Is it round? Does it have only one white sweet spot? If not you may want to use shooting group analysis to improve your shooting accuracy:
Since the Heat Map will include shots from multiple sessions it is likely that it will contain different sights settings and is not suitable for sight adjustments. You should rather use the Windage and Elevation calculated per single session.
In order to access this view simply tap on the 'Thermometer' icon in the Sessions view.