What is the difference between simple diffusion and active transport?

Simple diffusion is the movement of a molecules from an area of high concentration to an area of low concentration across a semipermeable membrane. Diffusion happens in liquids and gases as their particles move randomly. Diffusion is important as it helps move substances in and out of cells. We use simple diffusion to allow carbon dioxide and oxygen go in and out of our cells without the use of energy. Active transport is the movement of molecules from an area of low concentration to an area of high concentration so against the concentration gradient. Active transport requires energy as it involves moving molecules against their concentration gradient. We use active transport in our body when we want our cells to take up glucose.