Answer: population density
Step-by-step explanation:
The description of the map shows that it describes population density which is the number of people who live per square kilometer. Population density is usually higher for urban areas than it is for rural areas because there are many more people in urban areas than in rural.
Countries with a large population and a small area will also have high population density such as Nigeria whilst areas with a relatively low population but a large area will have a lower population density for instance, Russia.