A kitel (Yiddish for “gown”) is a white robe, traditionally worn by the Ashkenazim. It is also traditionally only worn by men; although some women today have become accustomed to wearing the kitel. The robe is worn over one’s clothing and is adorned with a white belt and a lace collar. While the kitel used to be worn every Shabbat for services, today it is only worn on High Holidays and special occasions. The kitel is a mark of new beginnings, thus Jews tend to wear the kitel during Passover Seder and at weddings. Some Jews also chose to be buried in a kitel, wrapped as a shroud.
The kitel is symbolically white to represent one’s return to purity and forgiveness. This is why many Jews believe it is appropriate to wear the kitel during the High Holidays (Rosh Hashanah and Yom Kippur) in the time of atonement. It is during this time that Jews ask God to absolve any transgressions committed within the past year and to cleanse their souls. For the reason that the kitel is also used as a shroud, it emblematically reminds Jews of the solemnest of the High Holidays.
Sources: Eisenberg, Ronald L. The JPS Guide to Jewish Traditions. PA: Jewish Publication Society, 2004; Wigoder, Geoffrey , Ed. The New Standard Jewish Encyclopedia. NY: Facts on File, 1992; Kolatch, Alfred J. The Jewish Book of Why/The Second Jewish Book of Why. NY: Jonathan David Publishers, 1989.