Diffusion follows the concentration gradient it implies that the flow of substances is from the region of higher to lower concentration. Besides, Factors like pressure also affect diffusion.

Diffusion occurs due to the random movement of particles. It usually happens due to a concentration gradient, meaning that molecules move from an area of high concentration to an area of lower concentration.Diffusion is thus a passive process (meaning that it does not require the input of energy). A substance moves from an area of high concentration to an area of lower concentration. This movement continues until the concentration of the substance evens out. Once the concentration has evened out, the substance still moves but will no longer have a concentration gradient. This state is called dynamic equilibrium.
The factors which affects the rate of diffusion are -
1.Concentration: Diffusion of molecules is entirely dependent on moving from an area of higher concentration to an area of lower concentration. In other words, diffusion occurs down the concentration gradient of the molecule in question. If the difference in concentration is higher, then the molecules will go down the concentration gradient faster. If there is not as great of a difference in concentration, the molecules will not move as quickly and the rate of diffusion will decrease.
2.Temperature: Particles move due to the kinetic energy associated with them. As temperature increases, the kinetic energy associated with each particle also increases. As a result, particles will move faster. If they can move faster, then they can also diffuse faster. Conversely, when the kinetic energy associated with the molecules decreases so does their movement. As a result, the rate of diffusion will be slower.
3.Solvent Properties: Viscosity and density greatly affect diffusion. If the medium that a given particle has to diffuse through is very dense or viscous, then the particle will have a harder time diffusing through it. So the rate of diffusion will be lower. If the medium is less dense or less viscous, then the particles will be able to move more quickly and will diffuse faster.
4.Solvent Properties: Viscosity and density greatly affect diffusion. If the medium that a given particle has to diffuse through is very dense or viscous, then the particle will have a harder time diffusing through it. So the rate of diffusion will be lower. If the medium is less dense or less viscous, then the particles will be able to move more quickly and will diffuse faster.

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration. It happens in liquids and gases because their particles move randomly from place to place.
Factors affecting the rate of diffusion are concentration gradient, temperature, and size of diffusing material.
The greater the difference in concentration, the more rapid the diffusion. The reverse is true for lighter molecules.
Heavier molecules move more slowly, therefore, they diffuse more slowly. The reverse is true for lighter molecules.
Higher temperature increases the energy and therefore the movement of molecules increases the rate of diffusion. Lower temperatures decrease the energy of molecules, thus decreasing the rate of diffusion.