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 céilí dances are danced by formations (ceili) of couples of 2 to 16 people. Irish social dance is a living tradition, and variations in particular dances are found across the Irish dance community; in some places, dances are deliberately modified and new dances are choreographed.

You can see a photo of Typical irish dancers here.

http://www.socalirishdance.com/Irishstepdance.php