The festival is observed by the kindling of the lights of a special candelabrum, the Menorah or Hanukiah, one light on each night of the holiday, progressing to eight on the final night. An extra light called a shamash, (Hebrew: "guard" or "servant") is also lit each night, and is given a distinct location, usually higher or lower than the others. The purpose of the extra light is to adhere to the prohibition, specified in the Talmud (Tracate Shabbat 21b-23a), against using the Hanukkah lights for anything other than publicizing and meditating on the Hanukkah story. (The shamash is used to light the other lights.)
Information is courtesy of Wikipedia
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