Self-Determination is a theory of human motivation developed by psychologists Edward Deci and Richard Ryan. Motivation, in this context, is what moves us to act.  The theory looks at the inherent, positive human tendency to move towards growth, and outlines three core needs which facilitate that growth. Those needs are Autonomy, Competence and Relatedness.
Competence – The need to experience our behaviors as effectively enacted (to feel like we’ve done a good job). 
Autonomy – The need to experience behavior as voluntary and “…reflectively self-endorsed”  (to feel like we have control over what we do).
Relatedness – The need to “…interact, be connected to, and experience caring for others”  (to have meaningful relationships and interactions with other people).
Here’s why these needs are so critical: SDT outlines two types of motivation, intrinsic and extrinsic. The three needs promote intrinsic motivation. This type of motivation initiates “behavior for its own sake,” because it’s inherently satisfying or engaging.  That innate human tendency to move towards growth, mentioned earlier is, essentially, intrinsic motivation.
On the flip side, extrinsic motivation initiates behavior for the sake of getting a reward (more on this later) or achieving an external goal. While extrinsic motivation doesn’t automatically lend itself to the satisfaction of the three core needs, SDT defines different types of extrinsic motivation that can (through a process called internalization) ultimately provide support for them. 
Back to the idea of rewards – within this concept of extrinsic motivation, there are both extrinsic and intrinsic rewards.
An extrinsic reward is tangible – like a salary raise, for instance. An intrinsic reward is intangible and internal, like getting a sense of recognition through praise from your boss. It’s helpful to understand this distinction because it is easy to confuse intrinsic motivation with intrinsic rewards. A simple way to remember it is that motivation always relates to the behavior or activity, and rewards are always an outcome. So, rewards (whether they’re intrinsic or extrinsic) fall under extrinsic motivation.
How can all of this be applied to work motivation?
A firm grasp on Self-Determination Theory is invaluable in the context of work performance optimization, as well as job satisfaction. SDT is often applied to the workplace, and a very real link has been found between work environments that support the three core needs and positive work-related outcomes.  The theory can help employers understand how best to develop and engage their people, and can help individuals understand how they can be successful professionally.
To tie it all together, extensive research around SDT has determined that the examination of different types of motivation and how they support the three core needs (Autonomy, Relatedness and Competence) is critical for an individual’s ability to grow and prosper. This is useful information in many contexts, including the professional world.
Discover how to leverage Self-Determination Theory to optimize your workplace via People Intelligence:
1. Deci, E. L., & Ryan, R. M. (n.d.). Home. Retrieved February 13, 2018, from http://selfdeterminationtheory.org/
2. Niemiec, C. P., & Ryan, R. M. (2009). Autonomy, competence, and relatedness in the classroom: Applying self-determination theory to educational practice. Theory and Research in Education, 7, 133-144.
3. Baumeister, R.; Leary, M. R. (1995). The need to belong: Desire for interpersonal attachments as a fundamental human motivation. Psychological Bulletin. 117: 497–529. doi:10.1037/0033-2909.117.3.497. PMID 7777651.
4. Ryan, R (1995). Psychological needs and the facilitation of integrative processes. Journal of Personality. 63: 397–427. doi:1111/j.1467-6494.1995.tb00501.x.
5. Ryan, R. M., & Deci, E. L. (2000). Intrinsic and Extrinsic Motivations: Classic Definitions and New Directions. Contemporary Educational Psychology,25(1), 54-67. doi:10.1006/ceps.1999.1020
6. Olafsen, A. H. (2016). The implications of need-satisfying work climates on state mindfulness in a longitudinal analysis of work outcomes. Motivation and Emotion,41(1), 22-37. doi:10.1007/s11031-016-9592-4.