Human migration is people moving from one place to another. Migration can be within countries or between countries, and it often involves large groups of people. Humans are known to have migrated extensively throughout history and prehistory.
Sometimes, the movement is voluntary, but sometimes, people are forced to move. They may suffer warfare, religious and political persecution, famine, and other natural disasters.
When people are forced to move, they are refugees. Many refugees are illegal immigrants and more than half are children and women. They may live in extreme poverty, lacking food, shelter, clothing, education and medical care.