Flow is a term used in psychology to mean the mental state of a person completely immersed in an activity. It is an altered state of consciousness. The person is fully focused, performing actively and successfully. The situation is widely recognized by phrases like in the zone, in the bubble, on the ball, in the moment, wired in, in the groove. The performer almost loses touch with their surroundings: phrases like "lost to the world" reflect this mental absorption.

The term flow was given to this experience by a psychologist, Mihaly Csikszentmihalyi. He said it was completely focused motivation. The hallmark of flow is a feeling of spontaneous joy, even rapture, while performing a task. Flow is also described as a deep focus on nothing but the activity – not even oneself or one's emotions.

A flow state can be entered while performing any activity, although it is most likely to occur when one is wholeheartedly performing a task or activity for intrinsic purposes. Intrinsic purposes involve anything that someone does merely because they want to. Extrinsic activities will not cause flow to occur. Extrinsic activities are anything that someone does because there is some other force causing them to do it. Extrinsic activities will not cause flow to occur. Passive activities like taking a bath or even watching TV usually do not elicit flow experiences as individuals have to actively do something to enter a flow state. While the activities that induce flow may vary and be multifaceted, Csikszentmihályi asserts that the experience of flow is similar despite the activity.

Components of flow
Csíkszentmihályi identifies the following ten factors as accompanying an experience of flow:<ref name=Finding>Csíkszentmihályi, Mihály 1996. Finding flow: the psychology of engagement with everyday life. Basic Books.  [a popular exposition emphasizing technique]</ref>

 Clear goals. Expectations and rules are known and goals are attainable and within one's skills and abilities.  Moreover, the challenge level and skill level should both be high.
 Concentrating: a high degree of concentration on a limited field of attention (a person engaged in the activity will have the opportunity to focus and to delve deeply into it).
 A loss of the feeling of self-consciousness.
 Distorted sense of time, one's sense of time is altered.
 Direct and immediate feedback (successes and failures in the course of the activity are apparent, so that behavior can be adjusted as needed).
 A balance between ability level and challenge: the activity is neither too easy nor too difficult.
 A sense of control over the situation or activity.
 The activity is intrinsically rewarding, so there is an effortlessness of action.
 A lack of awareness of bodily needs (to the extent that one can reach a point of great hunger or fatigue without realizing it)
 Absorption into the activity, narrowing of the focus of awareness down to the activity itself, action awareness merging''.
Not all are needed for flow to be experienced.

Other factors 
Flow operates on both physical and mental tasks. It applies to dance, football, chess and many other areas where people perform tasks in well-defined competitive situations, but also in art where the situation may be much more open. Evidence about flow comes from interviews with people after various types of performance. Efforts are being made to develop ways of enhancing flow for personal and commercial benefit.

Some of the challenges to staying in flow include states of apathy, boredom, and anxiety. Being in a state of apathy is characterized by having little to no challenges in a situation. A person’s skill level is also characterized as apathy when the person has a general lack of interest in the task at hand. Boredom is a slightly different state in that it occurs when challenges are low, but one's skill level exceeds those challenges causing one to seek higher challenges. A state of anxiety occurs when challenges are so high that they exceed one's perceived skill level causing one great distress and uneasiness.

References 

Psychology