Havdalah (הבדלה) is a Jewish religious ceremony that marks the symbolic end of Shabbat and holidays, and ushers in beginning of the new week. In Judaism, Shabbat ends -- and the new week begins -- at nightfall. Havdalah may be recited as soon as three stars are visible in the night sky. Some communities delay the Havdalah until later, in order to prolong Shabbat. If for some reason one cannot make Havdalah on Saturday night, it may be observed as late as Tuesday evening.
Havdalah is normally recited over kosher wine or kosher grape juice, although other beverages (except for water) may be used if wine or grape juice are not available. On completion of the Shabbat, a special braided Havdalah candle with more than one wick is lit, and a prayer is recited. Spices, often stored in a decorative spice container, are handed around so that everyone can smell the fragrance. In the Sephardi community, branches of aromatic plants are used for this purpose. After Yom Kippur, a candle is used but not spices.
At the conclusion of Havdalah, the leftover wine is poured into a small dish and the candle is extinguished in it, as a sign that the candle was lit solely for the mitzvah of havdalah. Based on Psalms 19:9, "the commandment of the Lord is clear, enlightening the eyes," some Jews dip a finger into the leftover wine and touch their eyes or pockets with it. Because it was used for a mitzvah, the wine is considered a "segulah," or good omen. (reference - http://www.chabad.org/article.asp?AID=16240)
When a major holiday follows Shabbat, the Havdalah service is recited as part of the holiday kiddush. Two holiday candles are held together for Havdalah and are not extinguished, because putting out a flame is prohibited on holidays, in the same way that it is on Shabbat.
Some Hassidic Jews, particularly (though not exclusively) women, recite the Yiddish prayer God of Abraham before Havdalah. After the Havdalah candle, it is customary to sing "Eliyahu Hanavi" and bless one another with the words "Shavu'a tov" (Hebrew) or "Gutte Voch" (Yiddish) (Have a good week). In some households, the participants break into a dance.