The distinction can be better understood if you look at the energy of the fluid with respect to its motion. When the fluid is stationary, i.e when there is no motion, the fluid has no kinetic energy. Which means, the pressure in the fluid is solely due to the potential energy. This is the static pressure of that fluid. But when the fluid is in motion, the potential energy would decrease, while the kinetic energy would increase. Now there is a pressure acting along the stream. This is the dynamic pressure.
