What process caused the yellow salt water to move out from the dialysis tubing into the cup?

The movement of yellow salt water out of the dialysis tubing into the cup is due to osmosis, a process where water molecules move across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. In this case, if the cup contains a lower concentration of solutes compared to the yellow salt water inside the tubing, water will flow out to equalize the solute concentrations on both sides of the membrane. This process continues until equilibrium is reached or until the concentration gradient is sufficiently reduced.