When the performance (engagement) of some activity is the end in its own right. For example, I play a sport because I enjoy doing it and may have fond memories of doing it. Intrinsic motivation relates to the personal satisfaction one feels from doing the behavior.

Intrinsic Motivation

The user's level of investment in learning/task, in regards to personal ability, time and energy. Can also include:
- A design for challenge / flow state
- Flexibility in problem solving
- Mastery focus over achievement focus

University of Illinois at Urbana-Champaign

The measure and study of sustained interaction with the medium. Engagement is different from Motivation in that it focuses on the user's willingness to continue interacting, rather than what inspires or spurs them into action.

Engagement

Fredricks, J.A., Blumenfeld, P.C., Paris, A.H. School Engagement: Potential of the Concept, State of the Evidence (2002). Review of Educational Research. 74:1, 59-109

School Engagement: Potential of the Concept, State of the Evidence (2002)

Willingness and consistency in performing said task. Can also be seen as "positive conduct" or "participation" with regards to the task at hand. Usually measured by:
- Persistence
- Level of concentration
- Contributions made

Behavioral Engagement

Emotional response to the task at hand. This is usually in response to needs being met or ignored while interacting with the task. Responses to varying levels of emotional engagement can be:
- Happiness
- Anxiety
- Boredom

Emotional Engagement

Cognitive Engagement

Student engagement is defined as student involvement in meaningful educational activities, and is considered an indicator for student learning and educational development. 

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