Hanukkah is a Jewish festival commemorating the rededication of the Second Temple in Jerusalem at the time of the Maccabean Revolt against the Seleucid Empire. It is also known as the Festival of Lights.

Hanukkah is observed for eight nights and days, starting on the 25th day of Kislev according to the Hebrew calendar, which may occur at any time from late November to late December in the Gregorian calendar. The festival is observed by lighting the candles of a candelabrum with nine branches, called a menorah (or hanukkiah).

Source: Wikipedia