Diffusion is the movement of particles from a high to low concentration, while osmosis is the movement of water from a high particle concentration to a low particle concentration.
Osmosis then is the movement of water particles from which has water and from which has not and to provide it with the sufficient H2O.
Diffusion occurs because of the movement of molecules from the region of higher concentration to the region of lower concentration. This movement of molecules occurs due to a thermal motion.
