Generally speaking, when we say saline, we mean physiological saline, and there is not much difference between the two. But strictly speaking, saline is a solution of sodium chloride and water mixed together, and the concentration of sodium chloride inside can be high or low. Physiological saline is specifically a solution containing 0.9% sodium chloride, the same concentration as the body’s extracellular fluid, so it can be fed directly into the body’s blood vessels. Saline is widely used. If a person is sick and needs an infusion in the hospital, saline is generally used as a solution to expand the volume of the body and also as a solution, for example, when antibiotics are needed, saline is used to prepare the solution.