Diffusion:

Diffusion is the net movement of a substance from an area of higher concentration to the area of lower concentration i.e. along a concentration gradient.

Facilitated Diffusion:

Many molecules do not diffuse freely across cell membranes because of their size or charge. Such molecules are taken into or out of the cells with the help of transport-proteins present in cell membranes. When one of these transport proteins makes it possible for a substance to move down its concentration gradient (from higher to lower concentration), the process is called facilitated diffusion. The rate of facilitated diffusion is higher than simple diffusion. Facilitated diffusion is a type of passive transport: Facilitated diffusion is also a sport because there is no expenditure of energy in this process.