Dalton's Law states that in a mixture of gases, the total pressure exerted is equal to the sum of the partial pressures of each individual gas. Each gas in the mixture behaves independently, contributing to the overall pressure based on its own concentration and temperature. For example, if a container holds oxygen, nitrogen, and carbon dioxide, the total pressure inside the container is the sum of the pressures that each gas would exert if it occupied the entire volume alone. This principle is essential in fields like chemistry and engineering for understanding gas behavior in various applications.