What direction, in regards to concentration, does diffusion move particles across the membrane?

Diffusion moves the particles from region of higher concentration to the region of lower concentration

Explanation:

Diffusion is the phenomena in which particles move from the region of their higher concentration to the region of their concentration across a membrane until  equilibrium in their concentration is reached.

There are three different types of diffusion observed in biological systems. they are:

Simple diffusion: Type of diffusion in which simple lipophilic molecules move across the membrane down their concentration gradient.Facilitated diffusion: Type of diffusion by which macro molecules travel across the membrane down their concentration gradient but they need some carrier molecules which facilitate their movement.Osmosis: Specialized type of diffusion, in which water moves from a dilute solution to a concentrated solution i.e. solvent moves down its concentration gradient, across the semipermeable membrane.