Population is a defined group of individuals, typically human, categorized by shared characteristics or geographic location. As a research concept, it serves as a fundamental unit for investigating the size, composition, distribution, and dynamics (e.g., growth, migration, mortality) of such collectivities over time. Its key characteristics include its quantifiable nature and the explicit definition of the group's boundaries. Its significance lies in providing the basis for understanding collective phenomena, identifying trends, assessing risks, informing policy, and evaluating the impact of interventions on specific groups.