Blue notations are for the teacher only. They do not appear on the lab sheets. The movement of fluids from an area of greater concentration to one of lesser concentration in search of equilibrium is called diffusion. When diffusion takes place across a membrane we call it osmosis.
All cells rely on the process of osmosis to some degree.
In a salt - water relationship the salt is the solute and the water is the solvent. If the membrane is semipermeable, it will allow only certain things to move across it. Water can cross the membrane to reach equilibrium but salt can not. This lab uses the potato cell as the mechanism for observing fluid movement. Carrots can be substituted and also work well.