The difference between immigration and migration is that while immigration refers specifically to the movement of foreign nationals into a different country for permanent settlement, migration refers to the movement of people more generally, whether internationally or domestically and whether for temporary or permanent settlement, although the United Nations broadly specifies at least one year as the duration required for "migrant" status. The existence of foreign national's economic or social ties to a host country underpins the definitions of both immigration and migration.
Migration is subdivided into a number of categories.
Circular migration is the often, but not necessarily voluntary movement of migrants between countries. Circular migrants include workers who are brought in to satisfy a host country's labor demands. Labor migration such as this tends to be regulated by governments.
Forced migration, on the other hand, is not voluntary but rather necessary for survival. Those in this category include refugee victims of displacement, natural disaster, warfare and famine.
Irregular migration is a process by which migrants enter a host country illegally, that is, without the proper documentation or without following the regulated channels.
Migrants themselves are typically classified as follows:
- Documented (legal)
- Irregular (illegal)
- Economic, which are those seeking to improve their quality of life, including asylum seekers
- Skilled, which are economically desirable in the host country due to their professional specialization or qualifications; they will often be granted a limited duration work visa, albeit one subject to less restrictions than semi-skilled or unskilled migrant workers