The couple

Couple: A pair of equal but opposite forces whose lines of action do not coincide.

A couple contribute zero net force, but a non-zero net moment. In fact, the moment it contributes is the same, regardless of the pivot point.

Molecular Squeeze

When fluid molecules repel their neighbours in all directions, we get the phenomenon called fluid pressure.

This comic takes an atomic view of a fluid. See if it explains some of the properties of fluid pressure, e.g. pressure acts in all directions, and pressure increases with depth.