So whenever a liquid actually travels through some type of conduit, through some type of pipe, the individual liquid molecules actually collide with the walls of that conduit with the walls of that pipe. Now, when each individual liquid molecule collides with the wall, it exerts a force. And if we sum up all the individual forces that the liquid molecules exert and divided by the surface area of the wall of the conduit on which those forces actually act on, then we obtain the fluid pressure, also known as hydrostatic pressure. So, if we have any fluid moving along the following conduit, then the liquid molecules exert a force on the walls of that conduit, as shown in this diagram. And if we take the sum of all these forces, if we find the net force due to all the liquid molecules and divided by the surface area of the wall of the conduit on which those forces act on, then we get the hydrostatic pressure. So notice these two pressures are not exactly the same thing.