The Chanukah lights can either be candle flames or oil-fueled. Since the miracle of Chanukah happened with olive oil – the little cruse of oil that lasted for eight days – an oil menorah is preferable to a candle one, and olive oil is the ideal fuel. Cotton wicks are preferred because of the smooth flame they produce. Source: Chabad
Hanukkah also romanized as Chanukah, Chanukkah, or Chanuka, also known as the Festival of Lights, is an eight-day Jewish holiday commemorating the rededication of the Holy Temple (the Second Temple) in Jerusalem at the time of the Maccabean Revolt of the 2nd century BCE. 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 the kindling of the lights of a unique candelabrum, the nine-branched Menorah or Hanukiah, one additional light on each night of the holiday, progressing to eight on the final night. The typical Menorah consists of eight branches with an additional raised branch. The extra light is called a shamash and is given a distinct location, usually above or below the rest. The purpose of the shamash is to have a light available for use, as using the Hanukkah lights themselves is forbidden. Read more at: Wikipedia