Motivation expresses our willingness to act for or against certain goals. So it explains why we do this or that or not. A distinction is made between the intrinsic motivation from ourselves (e.g. because we want something or want to prove something to ourselves) and the extrinsic motivation due to external influences (e.g. a reward or a salary increase).
Strictly speaking, motivation does not mean our behavior, but rather the reasons why we pursue a goal. In order to motivate yourself, you first need goals and, in the second step, the necessary drive and perseverance to achieve these goals. You can read more about it here.