What can be understood by the term ‘migration’?

What can be understood by the term ‘migration’? Give an example of a living organism which shows this phenomenon.

The regular seasonal journey undertaken by many species of animals and birds to escape the harsh and cold conditions of weather of a particular place is known as migration. Many animals, birds and fishes migrate to warmer regions in winter and come back when winter is over. Migration is marked by its annual seasonality. For example, the Siberian crane that comes from Siberia migrates to India at places like Bharatpur in Rajasthan and Sultanpur in Haryana.