Immigration is the voluntary movement of people from one country to another. They usually move with the aim of permanently settling in the adopted country. A closely related term is emigration. It refers to movement out of a country. When people depart their homelands for new homes elsewhere, they are said to be emigrants. Once they arrive in their new countries, they are known as immigrants. Another term, refugees, refers to people who have to flee their homes and go to other countries because they are in serious danger. Often they are victims of war or are being threatened because of their race, religion, or political beliefs.
Immigration is one form of the broader movement of peoples called migration. Migration, or moving from place to place, is as old as humanity itself. In prehistoric times humans lived largely by hunting. Groups of people migrated. They followed the animals on which their existence depended. Even when settled communities based on farming developed, people continued this movement. They experienced growing populations, crop failures, or the pressure of neighboring peoples. So they moved and cultivated new lands.