What is facilited diffusion?

Answer 1

Facilitated Diffusion is the movement of molecules across cell membranes through protein channels and carrier proteins.
Facilitated diffusion is a passive transport process, aka no energy required, where substances move down their concentration gradient (high concentration to low concentration) across a protein through a membrane protein because it is unable to diffuse directly through the phospholipid portion of the membrane itself.
Diffusion of molecules assisted by protein channels that pierce a cell membrane

Answer 2

Facilitated diffusion (or facilitated transport) is a process of diffusion, a form of passive transport facilitated by transport proteins. Facilitated diffusion is the spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane transport proteins. The facilitated diffusion may occur either across biological membranes or through aqueous compartments of an organism.