Chanukkah is the 'Festival of Lights'.
It celebrates the time when the Temple was besieged and there was only enough oil to light the altar for one day. By a miracle, the oil lasted for 8 days - hence, the 8 day festival. It is customary to give gifts & money (and those gold foil, chocolate coins) every day, of the 8 days. The holiday started Saturday (21st) at sundown and lasts until the 29th.