The Heatmap displays all the precincts in South Africa to you. Each precinct is colour coded.
The number of total crimes for the category or categories you have chosen are sorted numerically and then divided into 5 blocks, called quintiles.
The first quintile contains the precincts in the bottom 20%, so they have the least crimes. They are shown in green.
The fifth quintile contains the precincts that have are in the top 20% in terms of number of crimes, in other words they have the most crimes. They are shown in red.
Therefore the colour of the precinct, from green to orange to red, indicates how many crimes it has in comparison to the others.