Noun: It refers to the movement of people or animals from one place to another, especially seasonally or for a particular purpose.
* Example: The annual migration of birds from the north to the south.
Verb: It means to move from one place to another, especially in search of work or better living conditions.
* Example: Millions of people migrated to the United States in the 19th century.
The context will determine which part of speech "migration" is.