Migration can be permanent, temporary, voluntary or forced. It can be international or internal.
Permanent migration is when someone moves from one place to another and has no plans to return to their original home. Temporary migration is limited by time. This could be for seasonal employment. Forced migration involves the migrant having no choice but to move. Voluntatry migration is the opposite of this.
International migration is when a person moves from one country to another country. For example people moving from the UK to the USA. Internal migration is when people migrate within the same country or region. An example of this would be someone migrating from Manchester to London.