What is the difference between pump head and pressure?

Head is energy per unit weight of fluid, expressed in meters or feet of fluid, independent of fluid density. Pressure is force per unit area, measured in bar or psi, and depends on fluid density. They are related by: Pressure = Head x rho x g. Using head allows pump performance to be specified independently of the fluid being pumped - a pump develops the same head regardless of fluid density, though the pressure rise varies. This makes pump curves universal for any liquid.