Some examples of active transport are endocytosis, exocytosis and the use of a cell membrane pump; diffusion, osmosis and facilitated diffusion are all examples of passive transport. In active transport, particles move from areas of low concentration to high concentration, while in passive transport, the particles move from areas of high concentration to areas of low concentration.
Molecules want to move from areas of higher concentration to those with a lower concentration to maintain equilibrium. As a result, passive transport does not require an external source of energy. Since active transport goes against what molecules prefer to do, it requires a source of cellular energy, such as adenosine triphosphate.