Final answer:
Facilitated diffusion is a passive transport mechanism that allows substances to move down their concentration gradient through carrier proteins without the use of cellular energy.
Step-by-step explanation:
Facilitated diffusion is a type of passive transport. Unlike active transport, which requires energy to move substances against their concentration gradient, facilitated diffusion does not require energy from the cell. Instead, substances move down their concentration gradient through a carrier protein in the cell membrane, which facilitates their passage. Methods like ion pumps involve active transport because they require ATP to move substances, whereas facilitated diffusion relies on the natural motion of particles from an area of higher to an area of lower concentration, similar to passive diffusion and osmosis.