What are "kapparot"

Literally, kapparot means "atonement." Customarily on the eve of Yom Kippur, a man or boy takes in hand a rooster, a woman or girl takes a hen, and passes the fowl over the head three times while reciting a special prayer. The chicken is then ritually slaughtered and often given to the poor to use for their pre-Yom Kippur meal. The purpose of kapparot is to invoke sincere repentance through the thought that a similar fate as that awaiting the fowl might be due us for our sins, but through G-d's mercy and our true repentance it is averted.