What is diffusion and what are the factors that influence the rate of diffusion? What are some of the ways diffusion is used in the body? What is it called when water is diffused through a semi permeable membrane?

Diffusion is the spreading out of particles of any substance in solution or of gas resulting in a net movement of an area of high concentration to an area of low concentration. Diffusion is key to the survival of life on the planet and is essential for many processes such as gas exchange in the lungs and excretion of waste in the kidneys. 

Many factors can affect the rate fo diffusion but a concentration gradient, temperature and the surface area of the membrane are the main ones. Osmosis is the diffusion of water across a semi-permeable membrane.