Migration is the movement of people between or within countries.
Immigration is the movement of people into a country.
Emigration is the movement of people out of a country.
Push and pull factors
Push factors - negative things that make people want to move out of the place they're in. Negative things about the places they're leaving e.g. lack of jobs.
Pull factors - attract people to a new place. Positive factors about the place that they're moving to e.g. better facilities and job opportunities.
Obstacles and opportunities
Obstacles - things that make migration more difficult, e.g. the cost of moving.
Opportunities - opportunities that people encounter that mean they stop before they reach their intended destination.
Effects that encourage migration
Open door policies between EU members.
Ease of movement of an international elite - highly skilled or important people are in demand around the world. Globalisation means that they can go anywhere in the word to work.
Increased urban investment - investment from TNCs is often focused on urban areas, which can cause an increase in rural-urban migration as people move for new or better jobs.
Effects discouraging migration
There are restirctions on migration into an EU country if you're not from one originally, e.g. An American would find it hard to migrate to Europe.
Mexico and the USA are closely connected by the NAFTA trade bloc but this doesn't extend to the migration of people.