Suppose I have a fluid in a system like the one on the picture. The fluid is lower in one of the pipes because the pressure in this pipe is bigger than the atmospheric pressure. But is it then so that the pressure in the top of the water of pipe 1 equals the pressure of the water in the same level in pipe 2? I really have a hard time understanding pressure in fluids. I mean how can you talk about for instance the pressure being bigger in the bottom of a fluid because it is a rest - indeed the fluid is not at rest since the particles in it are continuously moving around..