Osmosis AS Biology cell states

Osmosis 

is the net movement of water from and area of high water potential to an area of lower water potential through a partially permeable membrane

Solute potential 

this is what the  concentration of dissolved substances is called and it is always negative as the water potential of pure water is 0 it is a measure of the reduction in water potential due to there being solutes in the water

Pressure Potential

when thee cell wall starts to become stretched it starts to try to stop swelling by resisting  the  water which is coming into the cell and as this develops you get pressure potential and  in most cases this value is positive 

a quick sum for you 

water potential…