The major components of population growth are birth rates, death rates and migration.
The natural increase of population is the difference between birth rates and death rates.
Birth Rate: Birth rate is the number of live births per thousand person in a year. It is a major component of growth, because in India birth rates have always been higher than death rates.
Death Rate: Death rate is the number of deaths per thousand persons in a year. The main cause of the rate of growth of the Indian population has been the rapid decline in death rates.
Migration Migration is the movement of people across regions and territories. Migration can be internal (within the country) or international (between the countries).
Internal migration does not change the size of the population, but influences the distribution of population within the nation.