The Hanukkah is a Jewish holiday when the Jewish people celebrate the liberation of Jerusalem from the Seleucid Empire in the 2nd century BC and the rededication of the second temple. It lasts for eight days, and is held anytime between late November and late December.
On the first day of the Hanukkah, Jewish families light one candle on a large candleholder called the menorah. The menorah is a large nine-branched candelabrum used in the Hanukkah. Each day, an additional candle is lit until all eight are burning. On the last day of the Hanukkah, all children in Israel have a day off from school.
The lights signify a miracle which happened in the 2nd century BC at the rededication of the temple in Jerusalem. The priests needed a large quantity of consecrated oil for the oil lamps. Unluckily, they only had one day's worth, but through a miracle the lamps burned for eight days, and the Jews had enough time to make more consecrated oil. That is why the festival lasts for eight days.