A population is the number of living people that live together in the same place. A city's population is the number of people living in that city. These people are called inhabitants or residents. The population includes all individuals that live in that certain area.The world population was estimated to have reached 7.5 billion in April 2017. Asia is the most populous continent, with its 4.3 billion inhabitants being 60% of the world population. The most populous country is China with 1.4 billion people.