Immigration is the act of foreigners

Alien (law)

In law, an alien is a person in a country who is not a citizen of that country.-Categorization:Types of "alien" persons are:*An alien who is legally permitted to remain in a country which is foreign to him or her. On specified terms, this kind of alien may be called a legal alien of that country...

 passing or coming into a country for the purpose of permanent residence. Immigration is made for many reasons, including economic, political, family re-unification, natural disaster, poverty or the wish to change one's surroundings voluntarily.
The International Organization for Migration

International Organization for Migration

The International Organization for Migration is an intergovernmental organization. It was initially established in 1951 as the Intergovernmental Committee for European Migration to help resettle people displaced by World War II....

 (IOM) stated there are more than 200-million migrants around the world today. Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

 hosted the largest number of immigrants, with 70.6 million people in 2005, the latest year for which figures are available.