Population distribution is a term that refers to where people live. Distribution refers to the fact that the area is inhabited. Population density is the term that refers to how many people are in an area.
Population distribution and density are usually notated by how many people live per square mile or square kilometer. For example, there can be 10 people or under per square mile in areas, such as Russia and parts of Africa. Some areas in Asia have 100 to 250 people per square mile. Generally speaking, the majority of the earth has 50 people or under living per square mile. Very few areas of the Earth are uninhabited with the exception of places like the Arctic.