A Hanukkah menorah, or hanukkiah, is a nine-branched candelabrum lit during the eight-day Jewish holiday of Hanukkah. Eight of the nine branches hold lights (candles or oil lamps) that symbolize the eight nights of the holiday; on each night, one more light is lit than the previous night, until on the final night all eight branches are ignited. The ninth branch holds a candle, called the shamash ("helper" or "servant"), which is used to light the other eight.

Source: Wikipedia