What transport is the movement of materials from lower concentration to higher concentration as in the processes of endocytosis and exocytosis.

Active transport requires ATP to enable a carrier protein to move from low concentration region to a higher concentration region.

While 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. Diffusion normally occurs between two compartments having difference in concentration. In case of fluid it moves from the region of higher concentration to the region of concentration until a balance is reached. The process of diffusion is very important for the humans as well. The oxygen that humans breathe in gets diffused with the blood.