Jews light candles on Hanukkah to commemorate the miracle of the oil in the Temple. After the Maccabees reclaimed and rededicated the desecrated Temple in Jerusalem, they found only enough ritually pure oil to light the menorah for one day, but it miraculously burned for eight days.
The Miracle
The holiday celebrates this event from the second century BCE, when a small cruse of oil lasted eight nights, allowing time to prepare more oil. This miracle, rather than just the military victory, became the focus through rabbinic tradition.
Lighting Procedure
A hanukkiah, a nine-branched candelabrum, is used: eight branches for the nights of Hanukkah and a central shamash (helper) candle to light the others without violating the rule against using the lights practically. Each night, one additional candle is lit, from one on the first night to all eight on the last, starting with the shamash.
Symbolism
The candles publicize the miracle, displayed in windows to remind others of Jewish faith and resilience. They represent increasing light against darkness, faith over assimilation, and divine intervention.