Densely populated areas are areas which have large numbers of people per km².

These are areas where there are many advantages for the people such as warmer climate, fertile soil and flat land.

Sparsely populated areas are areas which have small numbers of people per km².

These are areas where there are many disadvantages for the people such as extreme climates (too cold, too dry), infertile soil and lack of employment.

For example, the UK has densely populated areas in large cities and along good transport links, but sparsely populated areas along rugged coast lines and highland areas.

Also Brazil has densely populated regions close to large cities but sparsely populated regions in the tropical rainforest and areas which suffer drought.