The hot pot (huoguo) has a long history in China. It originated in the north, where people have to fend off the chill early in the year. It spread to the south during the Tang dynasty (A.D. 618-906). Later, northern nomads who settled in China enhanced the pot with beef and mutton, and southerners did the same with seafood. In the Qing dynasty, the hot pot became popular throughout the whole area of China.
Hot Pot used to be favored only in winter, but recently Hot Pot also appears on tables in other seasons. Some people especially like eating it in summer, sitting in front of a fire with an air-conditioner working behind and saying it couldn't have been better!
There are only two types of soup for a hot pot- one is Spicy and the other is not spicy (usually white in color). The base of the soup (either spicy or non spicy) varies from restaurant to restaurant- it is usually bone soup but chicken soup is also common. The flavored oil dip is NOT castor oil- it's sesame oil. And it can be 'dressed' up in a variety of ways according to your tastes- using vinegar, chicken powder, cilantro, chives, or a number of different things that are offered. If you have a mixed group- meaning some don't eat really spicy food...there are special pots with a divider in the middle and you can have both the non spicy and spicy soup. Usually if it's mixed- even the Chongqing people will boil vegetables in the non spicy side to cook them...and then just quickly dip them in the spicy side for more flavors.
The pot is made of brass with a wide outer rim around a chimney in which the charcoal burns to heat the soup. When the soup is boiling, dinners dip thin slices of frozen raw meat in the soup where it gets quick boiled and then put them into a kind of sauce like sesame or soy sauce, chili oil, and vinegar. The meat can be beef, mutton, chicken, fish, prawn, lots of things but not pork if you are in an Islamic restaurant. Vegetables such as mushrooms, bean curds can be quick boiled as well. Of course, you can also try whatever you like.