On Yom Kippur, the Torah instructs us to "afflict" ourselves, which means abstaining from an assortment of physical pleasures. There are two reasons for this: a) On this day, when our connection to G‑d is brought to the fore, we are compared to angels, who have no physical needs. b) We afflict ourselves to demonstrate the extent of our regret for our past misdeeds. (Click here for a more mystical explanation.)

Instead of focusing on the physical, the majority of the day is spent in the synagogue, devoted to repentance and prayer.

There are five areas of pleasure that we avoid on Yom Kippur—from sundown on the eve of the holiday until the following nightfall (click here to find out when Yom Kippur starts and ends in your location):

1. Eating or drinking.
2. Wearing leather footwear.
3. Bathing or washing.
4. Applying ointment, lotions, or creams.
5. Engaging in any form of spousal intimacy.

(These all are restrictions unique to Yom Kippur; we also abstain from all creative activities forbidden on the Shabbat, e.g., turning on lights, driving, and carrying in the public domain.)

It is also customary not to wear gold jewelry on Yom Kippur, as gold is reminiscent of the sin of the Golden Calf, and on the Day of Atonement – the day when we were forgiven for that egregious sin – we do not want to "remind" the Prosecutor (Satan) of our past sins.

Click here for a more detailed treatment of the Yom Kippur laws.