Diffusion is the process that describes the movement of molecules from areas of high concentration to areas of low concentration.
Diffusion is the net movement of molecules from an area of high concentration to an area of low concentration. Diffusion is characterized by the movement of molecules along the concentration gradient which could be facilitated by other molecules. The rate of diffusion is determined by the nature of interaction between the molecule and medium. The medium and the molecule may be solid, liquid or gas.