Irish dancing or Irish dance is a group of traditional dance forms originating in Ireland which can broadly be divided into social dance and performance dances. Irish social dances can be divided further into céilí and set dancing. Irish set dances are quadrilles, danced by four couples arranged in a square, while céilí dances are danced by varied formations (céilí) of two to sixteen people. In addition to their formation, there are significant stylistic differences between these two forms of social dance. Irish social dance is a living tradition, and variations in particular dances are found across the Irish dancing community; in some places, dances are deliberately modified and new dances are choreographed.
Irish dancing, popularized in 1994 by the world-famous show Riverdance, is notable for its rapid leg and foot movements, body and arms being kept largely stationary.
Most competitive dances are solo dances, though many stepdancers also perform and compete using céilí dances. The solo stepdance is generally characterized by a controlled but not rigid upper body, straight arms, and quick, precise movements of the feet. The solo dances can either be in "soft shoe" or "hard shoe".
The dancing traditions of Ireland probably grew in close association with traditional Irish music. Although its origins are unclear, Irish dancing was later influenced by dance forms from the Continent, especially the Quadrille. Travelling dancing masters taught all over Ireland, as late as the 18th and early 19th centuries. During this time, places for competitions and fairs were always small, so there was little room for the Dance Masters to perform. They would dance on tabletops, sometimes even the top of a barrel. Because of this, the dancing styles were very contained, with hands rigid at the sides, and a lack of arm movement and travelling across the stage. As time went on, larger places for dance competitions and performances were found, so styles grew to include more movement, more dancing across the stage as seen, for example, in Riverdance.
Irish social, or céilí /ˈkeɪli/ dances vary widely throughout Ireland and the rest of the world. A céilí dance may be performed with as few as two people and as many as sixteen. Céilí dances may also be danced with an unlimited number of couples in a long line or proceeding around in a circle (such as in "The Walls of Limerick", "The Waves of Tory", "Haymakers Jig", "An Rince Mor" or "Bonfire Dance"). Céilí dances are often fast and some are quite complex ("Antrim Reel", "Morris Reel"). In a social setting, a céilí dance may be "called" – that is, the upcoming steps are announced during the dance for the benefit of newcomers. The céilí dances are typically danced to Irish instruments such as the Irish Bodhran hand drum or fiddle in addition to the concertina (and similar instruments), guitar, whistle or flute.
The term céilí dance was invented in the late 19th century by the Gaelic League. Céilí as a noun differs from the adjective céilí. A céilí is a social gathering featuring Irish music and dance. Céilí dancing is a specific type of Irish dance. Some céilithe (plural of céilí) will only have céilí dancing, some only have set dancing, and some will have a mixture.
http://en.wikipedia.org/wiki/Irish_dance