Although human migration has existed for hundreds of thousands of years, immigration in the modern sense refers to movement of people from one nation-state to another, where they are not citizens. Immigration implies long-term permanent residence by the immigrants. Tourists and short-term visitors are not considered immigrants. However, seasonal labour migration (typically for periods of less than a year) is often treated as a form of immigration. The global volume of immigration is high in absolute terms, but low in relative terms. The UN estimated 190 million international migrants in 2005, about 3% of global population. The other 97% still live in the state in which they were born, or its successor state.
More often, people migrate due to economic reasons. Sometimes political, religious and personal factors are also responsible. The reasons of attractive incentives for migration are known as Pull factors and the compelling circumstances forcing Migration are known as Push factors which are mainly the reasons for Emigration from the country of origin. The push factors may be war, poverty, natural disasters etc. And pull factors may be political stability, higher incomes, family reasons.
Immigration Law is the law which exclusively governs immigration in a nation. So far as foreign citizens are concerned, Immigration Law is related to Nationality Law of a nation governing the matters of citizenship. International Law regulates Immigration Law concerning the citizens of a country. In this regard the United Nations International Covenant on Civil and Political Rights is relevant. The International Organization for Migration is the main intergovernmental organization in the field of Migration. It was initially formed in 1951 as the Intergovernmental Committee for European Migration to help the people displaced during the Second World War. This Organization is committed to the promotion of humane and orderly migration for the benefit of all.