I feel like the more deeply I am studying about fluids in physics, the more I realize that I don't really understand the basic concept of fluid pressure. Like firstly what is meant by fluid pressure? Is it the pressure/force that fluid molecules apply on EACH OTHER, as they collide with each other innumerable times? Is it the pressure that is felt by the SIDES and BOTTOM of the container housing the fluid molecules or the OBJECTS (whether it is person swimming or boat) submerged in the fluid, when the fluid particles are colliding with their surface area?
Also how does gravity contribute to fluid pressure? Like I keep reading that fluid pressure is greater in the bottom of the container housing the fluid than at the top of the container, because the weight of fluid particles at top is pushing downwards on the particles at the bottom. But why is that the case really? Aren't fluid molecules colliding the same way (like same number, force of collisions), irrespective of whether they are in the bottom, middle or top of the container? Also we know that fluid particles (more so gas particles than liquids) are always in motion, then with this in mind would it be correct to assume, that in a container of fluid, lots of fluid particles bottom of container might always randomly travel (like travel a vertical distance up and thus exchange vertical positions) to the near top or middle of the container, thus sometimes transmitting pressure from bottom to top and then top to bottom of container (because of course particles/molecules are always colliding) all the time? If this assumption of mine is correct that, then where does the concept of fluid pressure increasing with greater depths come from?
I don't know if my assumptions in the foregoing paragraph are faulty and that is the reason why my understanding of fluid is skewed, but if any one can gives any sort of explanation of this topic, it would be great.