Final answer:
Facilitated diffusion allows substances to move across the cell membrane down their concentration gradient without the use of energy, unlike active transport which requires ATP.
Step-by-step explanation:
Facilitated diffusion does not require energy. It is a process that enables hydrophilic molecules and ions to pass across a membrane with the aid of specific membrane proteins such as channel proteins and carrier proteins. These proteins help substances move along their concentration gradient, from an area of higher concentration to an area of lower concentration, without the need for cellular energy. This is in contrast to active transport, which does require energy, usually in the form of ATP, to move substances against their concentration gradient.