This is an example of a choropleth map. From the map we can see the percent of teeth that have been extracted due to tooth decay or gum disease for 2006, 2008 and 2010. A large percent of teeth extractions occurred in southern states indicated by the counties in red compared to Western states indicated by the counties in yellow.
Interestingly, the South is known for having poorer health outcomes and higher rates of chronic disease. Maps like this allow for this information to be displayed in a picture.