What is the difference between diffusion and active transport?

Diffusion is the spreading out of particles in solution or gas, from an area of high concentration to an area of low concentration. Because this movement is from high to low concentration this is down the concentration gradient. An example would be movement of oxygen from the lungs into the blood. It does not require energy Active transport still involves the movement of particles, but this time from an area of lower concentration to an area of higher concentration - the opposite direction to diffusion. This requires energy, from respiration. One example might be a plant transporting nutrients into its roots, where there is more of the nutrient inside the root than in the soil. It is important to learn these definitions for the exam! (Define keywords if necessary e.g. concentration, in solution)