The Prevent Intersection property is used to avoid overlapping between series labels and with the borders of rendered values and axes. By default, the Prevent Intersection property is set to false and series labels may overlap, what makes them look bad or unreadable. The picture below shows an example of a chart, with the Prevent Intersection property set to false:
If the Prevent Intersection property is set to true, then the series labels will not overlap. The picture below shows an example of a chart, with the Prevent Intersection property set to true:
