Explain the two main types of passive transport?

Passive transport is a movement of ions and other atomic or molecular substances across cell membranes without need of energy input. 

The two types are:
1. Diffusion
2. Facilitated Diffusion

Diffusion is the net movement of material from an area of high concentration to an area with lower concentration.

Facilitated diffusion is the movement of molecules across the cell membrane via special transport proteins that are embedded in the plasma membrane by actively taking up or excluding ions.

Basically, diffusion is like tipping over an hour glass and letting some but not all of the sand go to the other side. It is balanced and neither is more packed with "sand" then the other.

Facilitated diffusion is if the "sand" got sucked up in little bubbles and carried to another place then dropped off.