How does osmosis and diffusion work?

Osmosis and diffusion are two words used to describe the movement of molecules. Molecules are like people. They don't like to be squashed into small areas with lots of other molecules surrounding them. Molecules move to bigger areas with less molecules around them. This movement is called "moving down the concentration gradient". The concentration gradient is a measure of how many molecules are in one area compared to another. 

Diffusion: is the movement of molecules from a region of high concentration (lots of molecules present) to a region of low concentration (few molecules present) down the concentration gradient. It applies to molecules which are solids, liquids or gases. 

Omosis: is the movement of water molecules from a region of high concentration to a region of low concentration, down the concentration gradient, through a semi permeable membrane (this means it will block some molecules from moving through it but not others).