During Hanukkah, on each of the eight nights, a candle is lit in a special menorah (candelabra) called a 'hanukkiyah'. There is a special ninth candle called the 'shammash' or servant candle which is used to light the other candles.
A Chanukah menorah candles
(also known as a chanukiah candles) have nine candles: eight candles in a row, and one helper candle, known as a shamash, which is set apart from the others.
Every night of Chanukah, we kindle an additional light. So on the first night, you light the shamash and one more. On the second night, the shamash plus two are burning. By the time the eighth and final night of Chanukah rolls around, there are nine candles burning: the shamash plus all eight Hanukkah candles.