The two processes are diffusion and active transport.
Diffusion is the process where a substance moves from a high concentration to a low concentration. This can be referred to as going down a concentration gradient.
Active transport is process where a substance moves from a low concentration to a high concentration using energy. The best way to explain why this process requires energy is imagining going up a hill (low concentration to high concentration). It will require a lot of energy. Well, at least for me it does!