Yom Kippur, which translates to the Day of Atonement, is the holiest day of the Jewish Year. It's a serious holiday. The point is to ask G-d and your fellow humans for forgiveness so you can start the year with a clean slate, and deem yourself worthy of another year on earth. (NBD.) The intense period of reflection is accompanied by a 24-hour fast.

A cheat sheet to a holiday with such gravitas is a good idea for first-timers, so here are 10 things you should know about your first Yom Kippur.

1. Yom Kippur is the holiest day of the Jewish Year.

If you notice that your Jewish coworkers aren't in the office on Yom Kippur, that's because it is the holiest day on the Jewish calendar. This is the day that Jews ask G-d for forgiveness for all the sins they committed that year, and ask that their names be inscribed by G-d in the book of life for the year to come.

2. It's a chance for a clean slate.

Yom Kippur literally means Day of Atonement in Hebrew, and "atone" means to ask forgiveness. Unlike Catholics who confess their sins throughout the year, Yom Kippur is the one day prescribed for Jews to unload theirs. In addition to praying in temple for G-d's forgiveness, Jews also ask it of their fellow humans. The idea is that after observing the holiday, your slate is wiped clean and you can start the new year sin-free.

3. Fasting is involved.

There are multiple fast days in the Jewish calendar, but Yom Kippur is the most important. The directive comes straight from the bible, Leviticus 26:27, which directs Jews to "afflict their souls" on Yom Kippur. This has been interpreted by rabbis to mean fasting (which also means no drinking), although it also applies to other bodily pleasures, such as having sex, bathing, or otherwise making oneself smell nice.

4. But it just lasts a day.

Unlike Ramadan, which can last around a month and forbids eating from sunrise to sunset for that entire duration, Yom Kippur lasts just one day, but it is a full, 24-hour affair — sundown to sundown. If you find yourself back at the house before the rest of the congregation (some families send a few people back to the house to prepare the food for everyone else, so it's ready right at sundown), do not eat until sunset has happened or until the host has given the green light. Yes, there are bagels out. Yes, they look so good. No, you should not have one — at least, not yet.

Also, the Jewish G-d is a reasonable one. If you're sick, elderly, frail, too young (under 12, bar mitzvah age), or recently had a baby, you can get a pass from fasting.

5. You shouldn't wish people a happy holiday.

Yom Kippur is a somber affair that's all about humility and contrition. So no "Happy Yom Kippur." Wishing someone an easy fast is the right way to acknowledge this holiday.

6. The fasting period is bookmarked by eating.

It's typical to sit down to a substantial meal the afternoon before Yom Kippur, and to end the fast when the sun goes down the following day. This meal is called a "break fast." Usually, families and friends gather at home after temple and feast on comfort food. Depending on who's hosting, you may encounter a light meal of chicken soup with kreplach (meat-stuffed dumplings), tea, and something sweet, or a full-on spread of bagels, tuna and egg salads, smoked fish, and assorted desserts. If you're invited as a guest to a break fast, ask the host if you can bring something — a babka is never a bad idea.

7. People will be wearing white.

If you go to services for Yom Kippur, you may notice that many congregants will be wearing flowing white clothing. There are a few reasons for this. The white clothing is reminiscent of a burial shroud, and meant to remind observers of their mortality. It also symbolizes purity and mercy, and alludes to angels, which Jews try to emulate on the holiday.

8. And sneakers.

Luxury items are not permitted on Yom Kippur, which, in addition to other things, means no leather shoes. This translates to lots of sneakers (and even — gasp — Crocs!) with suits.

9. That horn is called a shofar.

Services generally end with a long blow from the shofar. It's done to celebrate victory over the prosecuting angel, express hope for the future, let people know it's time to prepare for the meal, and a few other reasons.

10. There's an art to breaking the fast.

It's a rookie move, but it happens all the time. Folks chow down after fasting and often feel pretty ill as a result. If you're fasting, ease back into noshing after going a day without by choosing light foods and drinking plenty of liquids. Remember: Chew a lot and eat slowly.

Are you fasting for Yom Kippur this year?