Explainer: What Is Migration?

What Is Migration?

What is the definition of “migrant”?

A migrant is someone who moves away from their home residence, either to a new place within their own country or to another country. ¹

Why do people migrate?

Migration exists on a continuum from voluntary migration to forced migration.

• 1International Organization for Migration, “About Migration,” IOM UN Migration website (iom.int).

People who migrate voluntarily can freely choose whether to migrate or not, and they might decide to move for work, to be near family, or to study. People who are forced to migrate have very little alternative except to leave their homes. For example, their lives may be threatened by war, natural disaster, or persecution if they stay. Many migrants fall somewhere in between the two extremes of the continuum, meaning there could be conditions that make it difficult to stay where they are, but they also have some degree of choice about whether or not to leave. ¹

The following model shows how people might decide to migrate and then become migrants. ²

1. Current conditions do not match desired life: The migration journey often starts when a person’s current life does not match the life they want to lead. This disconnect can be extreme; for example, a person’s life is threatened by war where they currently live. It can also be less extreme; for example, a person wants to get additional job training or education that is not available near their home.
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2. Decision to make a change: The person then decides what change they want to make to get closer to the life they want to lead, whether that is migration or a different change. For example, one person might be able to switch jobs and make a higher salary without moving, while another person might decide they need to move to a different city or country to find a job with better pay.
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3. Navigation of migration process: If the person decides to migrate, they have to navigate the complexity of the migration process—for example, the financial cost of a move, the process of getting a visa, or any dangers during the journey to a new place. Some people might want to migrate but are unable to do so.

What is the difference between international migration and internal migration?

Internal migration refers to any movement of people away from their home residence to a new residence within the same country. For example, if someone in the United States moves from Ohio to Arizona, they would be an internal migrant. Internal migration is much more common than international migration. It is also very difficult to measure internal migration around the world, since not all countries publish data on it. 

International migration refers to any movement of people away from their home residence across an international border to a new country where they are not citizens. For example, if a student moves from Senegal to Germany to enroll in a university program, they would be an international migrant. 

In 2024, there were an estimated 281 million international migrants around the world, representing 3.6% of the world population. ³ In 2021, 6.39 million of the international migrants around the world were international students. ⁴ ​​​​​​​

According to Pew Research Center’s 2022 “Key facts about recent trends in global migration” report: 

The countries that have the most international migrants are generally not the same countries where international migrants make up the greatest share of the population. For example, while the U.S. has more migrants than any other nation, migrants only account for about 15.1% of the U.S. population—a smaller share than in 24 countries or territories with a total population of at least 1 million. ⁵

• 1International Organization for Migration, “Types of Movements,” EMM2.0 Programme website (emm.iom.int).
• 2M. McAuliffe and L. A. Oucho, eds., World Migration Report 2024, International Organization for Migration (IOM), 118.
• 3IOM World Migration Report 2024, 8.
• 4IOM World Migration Report 2024, 40.
• 5Anusha Natarajan, Mohamad Moslimani, and Mark Hugo Lopez, “Key facts about recent trends in global migration,” Pew Research Center, December 16, 2022.

What is the difference between immigration, emigration, and return migration?

Immigration refers to the process of moving to a new country. For example, if a person moves to South Africa from Zimbabwe, they are an immigrant to South Africa.

Emigration refers to the process of moving away from a person’s home country. For example, if a person moves from Afghanistan to Iran, they are an emigrant from Afghanistan, and at the same time they are an immigrant to Iran.

Return migration refers to when a person moves back to their home country after a period of living in a different country. For example, if a person returns to Venezuela after living in Colombia for two years, they are a return migrant to Venezuela.

What is the difference between a refugee, an asylum seeker, and an internally displaced person?

Refugees are people who are outside of their own country and will not or cannot return because of a “well-founded fear of being persecuted for reasons of race, religion, nationality, membership of a particular social group or political opinion.” ¹ While in everyday language, the term refugee is sometimes used more broadly to refer to “a person fleeing life-threatening conditions,” ² under international law, it has a specific definition and set of criteria that individuals must meet. For example, a Syrian person who flees to Turkey because they fear they will be killed due to their political beliefs is a refugee. The definition also includes “stateless” people, who are not recognized as citizens of any country. People can become stateless for a variety of reasons, including if they are not registered at birth, they are born to stateless parents, or they are born in a country where women cannot pass on citizenship and their father is unknown. 

Asylum seekers are people who are asking for protection under international law. Usually, an asylum seeker arrives in a foreign country and applies for protection under that country’s asylum laws. Each country has a different process for granting asylum. People applying for asylum are usually asked to supply evidence—for example, the harm they suffered and why they were the target of harm—along with their application. Under international law, people have the right to seek asylum in a different county if their own government fails in its obligations to them. People who are granted asylum are refugees under international law.

Internally displaced persons (IDPs) are people who are forced to flee their home but stay within their own country. An IDP might be forced to migrate for the same reasons as a refugee, but a person can only be a refugee if they cross an international border.

• 1United Nations High Commissioner for Refugees (UNHCR), “Convention and Protocol Relating to the Status of Refugees.”
• 2Andrew E. Shacknove, “Who Is a Refugee?,” Ethics 95, No. 2 (1985): 274–84.