Final answer:
Diffusion is a passive process of transport where substances move from an area of high concentration to an area of low concentration until the concentration is equal across a space. It creates a concentration gradient between two regions.
Step-by-step explanation:
Diffusion is a passive process of transport. A single substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across a space. Diffusion creates a concentration gradient between two regions. It does not reverse or eliminate the concentration gradient, but rather moves substances from an area of higher concentration to an area of lower concentration.