A kittel (Yiddish: ?) is a white linen or cotton robe  worn by religious Jews on holidays, in the synagogue or at home when leading the Passover seder. Kittels are sometimes worn by grooms. It is also customary for Jews to be buried in a kittel.
In Judaism, married men wear a kittel in the synagogue on Yom Kippur. In egalitarian synagogues, religious Jews - both men and women - wear a kittel.  The wearing of a kittel on the High Holidays is symbolically linked to its use as a burial shroud, and, to the verse "our sins shall be made as white as snow" (Isaiah 1:18).Some wear a kittel when leading the Passover Seder.
In some communities, the cantor wears a kittel on the first night of Selichot, the seventh day of the Holiday of Sukkot (also known as Hoshanah Rabbah), the Musaf prayers of Shemini Atzeret and the first day of Passover, where the prayers for rain (Tefilat HaGeshem) and dew (Tefilat HaTal) are respectively recited.
In some parts of the Jewish world, the kittel is known as a sargenes, related to the Old French serge as well as Latin serica.
As a shroud, the kittel signifies simple attire that assures equality for all in death. Because Jewish law dictates that the dead are buried without anything else in the coffin other than simple linen clothes, a kittel has no pockets.
The white color is said to symbolize purity, which partly explains its use during weddings. It is also felt to signify unity with the bride (who also wears white) and the beginning of a new life together. Another reason it is worn at the wedding is because it has no pockets, showing that the couple is marrying for love, not for what they possess.
Actually, a kittel --worn by some Jewish men at their weddings, on Yom Kippur, or when leading a Passover Seder --doesn't have to be made of linen. The website of the Judaica store Eichler's has a choice of 26 in either 100% cotton or a polyester/cotton blend, but none in linen.