Here is a simple explanation from Judaism 101:
Chanukah is the festival of lights, commemorating the rededication of the Temple in Jerusalem after a successful revolt against the Seleucid Greeks. As part of the rededication, the victorious Jews needed to light the Temple’s menorah (candelabrum), but they had only enough oil to last one day and it would take eight days to prepare more oil. Miraculously, the one-day supply of oil lasted for eight days. The miracle of the oil is commemorated with this eight-day candle lighting holiday.
Chanukah begins between Thanksgiving and Christmas. About half of the time, it overlaps with Christmas, but there are many years when Chanukkah ends long before Christmas. In 2002, for example, Chanukkah began on Thanksgiving and ended in the first week of December, but that is unusual.
Almost all Jews light candles with their families for at least some nights of the holiday, so people like to be at home during this holiday. Although almost nobody takes off from work or school for this holiday, many may not want to work nights or travel during the holiday so they can light candles with the family, and accommodations should be made for this.
Here are some links for more info and children’s activities: