A style of American theatrical dance. It is distinguished by percussive footwork that marks out rhythmic patterns on the floor. Normally, these sounds are emphasized using heavy shoes like the Irish clog or tap shoes (character shoes with metal plates attached at the heel and the ball of the foot).

Some of the common steps that make up the basis for all tap dancing are:
(ball refers to the ball of the foot, which can be considered the frontal padded area)
Brush - a scrape of the ball of the foot on the floor
Dig - a press of the ball onto the floor
Heel - a press of the heel onto the floor
Shuffle - a brush forward followed by a brush back
Slap - a brush forward followed by a dig
Flap - same as a slap, but the weight of the body shifts onto the foot performing the action
Pullback - a brush back followed by a dig

History
The forerunners of tap as it's known today include Irish step-dancing, clog dancing and native African dances. The former two merged with the latter into folk dancing, which was more like what can be considered "soft-shoeing," being performed in soft leather shoes. The dances evolved into two forms in the late nineteenth century. Buck-and-wing, a quick style done in heavy-soled wooden shoes, and the true soft-shoe style, which was slower.

By the 1920s, metal taps had been added to the leather shoes, and African-Americans (with whom the style was apparently the most popular) were adding to the growing number of dancing styles that incorporated the shoes. Jazz music added a new dimension rhythmically when it became popular, and eventually tap styles ranged from slow and syncopated to fast and acrobatic collections of movements which were quite technically difficult.

Persons Influential in Tap
Gene Kelly added ballet and modern dance moves to the traditional tap routines.
Prominent dance teams included Slap and Happy (Harold Daniels and Leslie Irvin) and Stump and Stumpy (James Cross and Harold Cromer).
Bill "Bojangles" Robinson became America's most famous tap dancer.
The slave dances were adapted theatrically in 1828 in the first blackface minstrel show, in the tap-like dancing of Thomas "Daddy" Rice.