Population refers to the total number of individuals living in a specific area, such as a city, country, or the entire world. It can include humans, animals, or plants, depending on the context. Population size can change over time due to factors like birth rates, death rates, and migration. Demographers study populations to understand their characteristics, such as age, gender, and ethnicity. This information helps governments and organizations plan for resources, services, and infrastructure. For example, knowing the population of a city can assist in determining the need for schools, hospitals, and public transportation systems.