Dance is a performing art form consisting of purposefully selected sequences of human movement. This movement has aesthetic and symbolic value, and is acknowledged as dance by performers and observers within a particular culture. Dance can be categorized and described by its choreography, by its repertoire of movements, or by its historical period or place of origin.Theatrical dance, also called performance or concert dance, is intended primarily as a spectacle, usually a performance upon a stage by virtuoso dancers. It often tells a story, perhaps using mime, costume and scenery, or else it may simply interpret the musical accompaniment, which is often specially composed. Examples are western ballet and modern dance, Classical Indian dance and Chinese and Japanese song and dance dramas.Rhythm and dance are deeply linked in history and practice. The American dancer Ted Shawn wrote; "The conception of rhythm which underlies all studies of the dance is something about which we could talk forever, and still not finish." A musical rhythm requires two main elements; first, a regularly-repeating pulse (also called the "beat" or "tactus") that establishes the tempo and, second, a pattern of accents and rests that establishes the character of the metre or basic rhythmic pattern. The basic pulse is roughly equal in duration to a simple step or gesture.