A carol is in Modern English a festive song, generally religious but not necessarily connected with church worship, and often with a dance-like or popular character. The verb caroling (or “to carol”) also refers to the singing of carols.
Today the carol is represented almost exclusively by the Christmas carol, the Advent carol, and to a much lesser extent by the Easter carol; however, despite their present association with religion, this has not always been the case.

see more at wikipedia

Check More at http://bit.ly/2qsXm7r