Water potential is the potential energy of water which helps in the movement of water. Pure water has the highest water potential , pure water has a water potential equal to zero. When solute is added to the water it decreases its water potential. As we know that the cell having greater water potential has more concentration of water thus we can say that the movement of water will take place from high water potential to low water potential, as diffusion of water takes place from its high concentration to low concentration. Thus the concept of water potential help us to understand in which direction the water will move. 

Osmotic pressure is equivalent to the osmotic potential but osmotic pressure is the positive pressure apllied whereas the osmotic potential is negative.

(i) Root pressure.

(ii) Transpiration pull.