There are three main visualization types in the IMS, Marker, Cluster and Heatmap. You switch between them using the icons on the right hand side of the map.
The cluster map shows the number of the incidents in the area surround area. You can set the radius of the clusters to increase or reduce the granularity of the data displayed on the map. This shows the distribution of incidents, though you don't get exact locations.
The marker map shows the incidents colour-coded by incident type. This shows incidents in their precise location, but will not shot incidents stacked on top of one other.
The heatmap shows the density of incidents in a given area. This gives a general assessment of the threat though doesn't show precise information. You can adjust the density radius, just like on the cluster map, and the intensity of the colour gradient.