Channukah is the eight day Jewish Festival of Lights, celebrating a miracle in the second century B.C.
In 171 B.C. Antiochus Epiphanus made a royal law that the Jews were to bow down and offer sacrifices to Zeus. Jews were forbidden to observe the Sabbath or study the Torah.
A family named the Maccabees led a successful revolt of a few thousand Jews against 20,000 Syrians. News of the defeat preceded them and when they came to the temple it was left empty and ransacked.
The Maccabees cleaned and rededicated the Temple, but when they went to relight the eternal lamp, they found only enough pure olive oil for one day. It would take the priest 8 more days to make more oil. Once lit, the eternal lamp is supposed to never be extinguished, but they lit the lamp anyway. Instead of the oil lasting one day it lasted for 8 days.
Celebration of this miracle became the Feast of Lights: Channukah. Later rabbis designed a special menorah with nine candles: eight candles for each day of Channukkah, and a tall central candle, the Shamash, representing the original holy lamp of the temple, and used to light the Channukah candles.