"Play is a rite and a quality of mind in engaging with one's worldview.
Play refers to a range of voluntary, intrinsically motivated activities that are normally associated with pleasure and enjoyment. Play may consist of amusing, pretend or imaginary interpersonal and intrapersonal interactions or interplay. The rites of play are evident throughout nature and are perceived in people and animals, particularly in the cognitive development and socialization of those engaged in developmental processes and the young. Play often entertains props, tools, animals, or toys in the context of learning and recreation. Some play has clearly defined goals and when structured with rules is entitled a game. Whereas, some play exhibits no such goals nor rules and is considered to be "unstructured" in the literature.
Concerted endeavor has been made to identify the qualities of play, but this task is not without its ambiguities. For example, play is commonly perceived as a frivolous and non-serious activity; yet when watching children at play, one can observe the transfixed seriousness and entrancing absorption with which they engage in it. Other criteria of play include a relaxed pace and freedom versus compulsion. Yet play seems to have its intrinsic constraints as in, "You're not playing fair."
When play is structured and goal orientated it is often presented as a game. Play can also be seen as the activity of rehearsing life events e.g. young animals play fighting. Play may also serve as a pretext, allowing people to explore reactions of others by engaging in playful interaction. Flirting is an example of such behavior. These and other concepts or rhetorics of play are discussed at length by Brian Sutton-Smith in the book The Ambiguity of Play. Sometimes play is dangerous, such as in extreme sports. This type of play could be considered stunt play, whether engaging in play frighting, sky-diving, or riding a device at high speed in an unusual manner.
The seminal text in play studies is Homo Ludens by Johan Huizinga. Huizinga defined play as follows:
Summing up the formal characteristic of play, we might call it a free activity standing quite consciously outside ‘ordinary’ life as being ‘not serious’ but at the same time absorbing the player intensely and utterly. It is an activity connected with no material interest, and no profit can be gained by it. It proceeds within its own proper boundaries of time and space according to fixed rules and in an orderly manner. It promotes the formation of social groupings that tend to surround themselves with secrecy and to stress the difference from the common world by disguise or other means.
This definition of play as constituting a separate and independent sphere of human activity is sometimes referred to as the "magic circle" notion of play, and attributed to Huizinga, who does make reference to the term at some points in Homo Ludens. According to Huizinga, within play spaces, human behavior is structured by very different rules: e.g. kicking (and only kicking) a ball in one direction or another, using physical force to impede another player (in a way which might be illegal outside the context of the game).
Another classic in play theory is Man, Play and Games by Roger Caillois. Borrowing much of his definition from Huizinga, Caillois coined several formal sub-categories of play, such as alea (games of chance) and ilinx (vertigo or thrill-seeking play).
According to Stephen Nachmanovitch, play is the root and foundation of creativity in the arts and sciences also as in daily life."
(quoted from wikipedia)