What is "the flow experience" and what does it have to do with motivation?
The flow experience is when a person is completely involved in what he or she is doing, when the concentration is very high, when the person knows moment by moment what the next steps should be, like if you are playing tennis, you know where you want the ball to go, if you are playing a musical instrument you know what notes you want to play, every millisecond, almost. And you get feedback to what you're doing. That is, if you're playing music, you can hear whether what you are trying to do is coming out right or in tennis you see where the ball goes and so on. So there's concentration, clear goals, feedback, there is the feeling that what you can do is more or less in balance with what needs to be done, that is, challenges and skills are pretty much in balance.
When these characteristics are present a person wants to do whatever made him or her feel like this, it becomes almost addictive and you're trying to repeat that feeling and that seems to explain why people are willing to do things for no good reason -- there is no money, no recognition -- just because this experience is so rewarding and that's the flow experience.