In active transport, a molecule is transported against its gradient which means the flow of molecule is from regions of low concentration to regions of high concentration. In order to carryout such transports, external energy is applied through biological pumps such as sodium-potassium pump (Na+/K+ ATPase) which maintains the resting potential of the cell.
Some times the energy produced by ATP is directly used and this process is known as primary active transport/diffusion
