What word describes what people do
when they spread out and live in almost
every land area of the world?

The process that has led to humans traveling and living in many parts of the world is called migration and human migration has led to the movement of people for centuries around the globe. Also the concept of dispersion means that something is spread far across a certain area such as humans around the world. 

Aregion is an area of land that has common features. these features can be natural, such as climate or landscape. they can also be artificial, such as language or religion. the xinjiang uyghur autonomous region, above, is an area of china inhabited by uyghurs, a muslim group with ethnic ties to turkish people.