It is a biological membrane, which functions by permitting the movements of certain molecules or ions to pass through it.
It is a barrier that will only allow some molecules to pass through while blocking the passage of other molecules.
(b) Osmosis:
It is a process by which the molecules of a solvent pass from a solution of low concentration to a solution of high concentration through a semi-permeable membrane
Osmosis is the spontaneous passage or diffusion of water or other solvents through a semipermeable membrane.