Simple and facilitated diffusion

Question

What is the basic difference among simple and facilitated diffusion? Facilitated by which kind of molecule does the word facilitated signify?

Answer 1

Simple diffusion is the direct passageway of substances across the membrane in preference of their concentration gradient. In facilitated diffusion the movement of substances is as well in favor of their concentration gradient however the substances move bound to particular molecules that performs as “permeabilizers”, that is, facilitators of their passage via the membrane.