Motivation is the term for the factors that direct and energize behavior.
There have been many approaches to explaining motivation. The instinct approach holds that motivations are caused by instincts, but most do not support this approach, since it is oversimplistic. The drive reduction approach holds that basic needs create drives, and motivation is the desire to reduce these drives. Primary drives satisfy biological needs, while secondary drives satisfy non-crucial needs. The arousal approach holds that people strive to maintain a constant level of stimulation and activity.