Chanukah is an eight day holiday that begins on the 25th day of Kislev. Chanukah is celebrated in memory of the victory of the Jewish rebellion against the Greek suppression of Judaism.
The Jewish rebellion against this oppression began as a small revolt led by the Chasmonean family, Mattityahu HaKohen and his five sons. When Mattityahu died he was succeeded by his son, Yehudah HaMakabee.
Yehuda led the Jews to victory, driving the Greeks out of Jerusalem. The Jews were then able to clean the Temple and to resume the Temple service. This took place on the 25th of Kislev.
At this point the famous "Miracle of Chanukah" took place. Part of the Temple service is the lighting of the Menorah. This requires ritually pure olive oil. Due to the Greek desecration of the Temple no such oil could be found except for one small container which contained enough oil to last for one day.
Since it would take eight days to get the required new oil this was a serious problem. The Jews used this oil for the first day and it miraculously lasted for the full eight days till new oil was available.
The Jewish victory celebrated on Chanukah was primarily a religious victory, it ended the suppression of Judaism. The holiday of Chanukah is named after the rededication of the Holy Temple, Chanukah means "dedication ceremony" or "inauguration".
The Chanukah Menorah has eight lamps in a perfectly straight line, plus a ninth lamp, the Shamash, which is separated from the others. A Menorah can be made from any material, but metal is best and silver is ideal. All oils and candles are acceptable for the Chanukah Menorah. Nevertheless, olive oil is the best.
The standard custom is to light one candle on the first night, two the second night, and so on, until the eighth night when eight candles are lit. The standard custom is for every member of the household to light their own Menorah.
The time for lighting the Menorah is at nightfall, when the stars come out. If one was unable to light at the proper time, he can still light. We are prohibited from using the Chanukah lights for anything, such as reading or lighting another fire.
On Friday afternoon, one lights the Menorah before the lighting of the Shabbat candles. Both must be lit before sundown. Care must be taken to provide enough oil in the Menorah (or large enough candles) that it will burn for a half-hour after nightfall.
It is prohibited to fast or to eulogize the dead on Chanukah. Some say that it is a mitzvah to have somewhat more festive meals on Chanukah. There is also a custom to eat dairy foods on Chanukah.
One should speak about the miracles of Chanukah with his family. It is customary to increase the amount of charity one gives on Chanukah, particularly to poor Torah scholars.
There is a tradition to play with a "dreidel" on Chanukah. A dreidel is a four-sided top with Hebrew letters distributed one to each side. These letters stand for the sentence: "Nes Gadol Haya Sham", which means "A Great Miracle Happened There."
It is a widely accepted custom to eat foods fried in oil on Chanukah. Some of the most common foods eaten on Chanukah are the potato Latke (pancake) and the Sufgania (donut).
At the time of the miracle of Chanukah, the risk was not to the bodily survival of the Jewish people but to the spiritual survival, Antiochus would have been quite satisfied with the Jews if they had, G-d forbid, left their faith.