That's a pretty good question. Chanukah isn't considered an important holiday in the Jewish religion, but it has been increased in status because it occurs near Christmas and may involve giving gifts. The marketers for toys and baubles want Jews to buy stuff too, so Chanukah has become a good excuse to encourage that.
Jewish children may also feel left out of the gift giving at Christmas. Our non-Jewish friends at school all had presents to show off and what did we get – a dreidel!
A dreidel is a small top with Hebrew letters on each side that indicated how much money you won for each spin. Historically it was used by Jewish men for gambling the way we would use dice today.
When Israel was occupied by the Hellenic Empire in Syria in 200 BC, the Greeks and Syrians did not permit Jews to gather for their religious services. The Temple was occupied by Greek soldiers to prevent the Jews from holding services there.
Chanukah celebrates the victory of a small band of Jewish revolutionaries over the Syrian and Greek occupiers who outlawed the Jewish religion and forced Jews to convert to the Greek religion of that time.
Jewish services required a minion, or 10 men, to hold a religious service. So the men would gather to gamble, which in those days meant betting on the spin of the dreidel. When soldiers came to check on these groups, the men would be gambling, which was legal, and not worshiping, which was illegal.
Years later children would be given a dreidel and "Chanukah gelt," or money, to use for playing the dreidel game. The money was either small change or chocolate wrapped in gold foil to look like coins. This gift of money evolved into presents to match those given to Christian children at Christmas. But Chanukah isn't a fun holiday. It represents the persistence of Jews in being Jewish.
The menorah or candle holder is used to represent the rededication of the Temple after defeating the Greeks. There was only enough holy oil left for one day, but the flame burned for 8 days. So the menorah has eight candles, one for each day the oil lamp lasted and one more that is used to light the increasing number of candles each night.
Why does Chanukah start at different times each year? That one's easy. Our current calendar is based on the Gregorian Calendar established by Pope Gregory XIII in 1582. The Hebrew Calendar originated around 200 AD and is best explained in an an article in Wikipedia.
The two calendars use different methods for calculating months and days. That's why Chanukah is sometimes close to Christmas and other times, like this year, a couple of week earlier.