Be yourself; everyone else is already taken. ― Oscar Wilde
Depends on where are coming from. To many it refers to Irish and Scottish music, but in Briton and the US it usually implies Irish music, especially traditional music. In Europe it comprises Breton & Galcian music as well. For others it refers to a certain genre of mood music for easy listening and relaxtion, and there are many "Celtic" music albums. And, for those not familiar with the term, the "C" in Celtic is pronounced like a "K", not an "S" as in the "Boston Celtics."