This document discusses pressure in both gases and liquids. It defines pressure as force per unit area and provides the formula P=F/A. It explains that pressure in liquids acts in all directions due to their density. The pressure in a liquid is calculated as P=ρgh, where ρ is the density of the liquid, g is gravitational acceleration, and h is depth. Some applications of pressure in liquids include water tanks, dams, submarines, and hydraulic systems, where the pressure increases with depth due to the density of the liquid and effects of gravity.