I've been asking around, and it seems like there are not many Jews on Tengaged or people who know about the Jewish customs, so I'll explain a little bit about one of them that starts at sunset tonight.
Yom Kippur is the biggest Jewish "holiday". During Yom Kippur, you atone for your sins. This means that for 25 hours from sunset tonight, you fast meaning NO EATING OR DRINKING. You also pray a ton. There's a prayer commencing it, a special morning prayer, a special afternoon prayer, and a special night prayer ending it.
After Yom Kippur, you are absolved from your sins. This is like confessing in Catholicism but it's a big yearly thing that all Jews follow.