Potential osmotic pressure

Potential osmotic pressure (POP) is the maximum osmotic pressure that could develop in a solution if it were separated from distilled water by a selectively permeable membrane. It is the number of solute particles in a unit volume of the solution that directly determines its potential osmotic pressure.

Cytoplasm is considered a cell's "solution." The liquid cytoplasm exerts pressure (force), per unit of surface, on the cell membrane. We call this force or pressure that is exerted the "hydrostatic pressure" of the cytoplasm.

What would happen to a cell's cytoplasm if you placed it into distilled water? It would osmose into the cell. This will increase the pressure inside the cell.

Osmotic pressure is simply the pressure measured as a particular moment during osmosis. If one waits until equilibrium then "osmotic pressure" would equal "P.O.P."