In food preparation, a crock-pot (also crock pot) is the name given by some manufacturers to their brands of slow cookers. It is a trademarked term in many countries, but is often used generically. When used to refer to the trademarked brand of cooker, both words are capitalized.
This type of slow cooker consists of a pot (typically 10" across and similarly high) made of fired clay and usually glazed, surrounded by a housing, usually metal, containing a thermostatically controlled electric heating element. A crockpot has a loosely fitting lid of glass or plastic to keep in the fluids. Cooking is done at atmospheric pressure and up to the boiling point of the fluid (typically 212 F / 100 C). Many crockpots have two settings for power. The physics of boiling prohibit a temperature of the contents above the boiling point while there is still liquid changing into stem (most of which condenses back into the crock).
In use, the food is placed inside the pot, immersed in water, the lid applied, and the unit switched on. Cooking times vary with the recipe and with the food quantity, but are typically several hours. Temperatures are low in comparison with traditional ovens, and with broiling and baking. Cooking is sufficiently slow that, if the food is not removed promptly at the specified time, little harm is done.
The water and its proper level is important, for it serves both as the heat conduction mechanism between the pot walls and the food, and as the flavoring (herbs and spices) distribution method and a 'basting' mechanism. No stirring is required (or allowed); removing the lid during cooking causes significant cooking delays. The lid is important as it prevents escape of hot water vapor which would, if permitted, lead to lowering the internal water level and to loss of heat.
Recipes for these cookers must be adjusted to compensate for the nature of the cooking. Often water must be decreased. Most (probably all) come with recipe booklets; many cookbooks and websites with crock pot recipes are available. A small number of cookbooks seek to make complete dishes in a crockpot using fewer than five ingredients while others treat the crockpot as a serious piece of culinary equipment capable of producing gourmet meals. With some experience, timings and recipe adjustments can be successfully made for many recipes not originally intended for these cookers.
Safety: Cooking temperatures are lower than many other cooking methods, and cooking times are lengthy, so some have been concerned about the growth of micro-organisms. If the temperature control is working correctly, and if food is not left to stand more than briefly at room temperature, there is little problem. Fill the pot, add water, and promptly turn the unit on; this will avoid such problems.
If the starting food ingredients are frozen, it may take a long time for the pot to rise to proper cooking temperature. During this prolonged temperature climb, the microbes in the food can multiply. The microbes will be eventually entirely killed before the food is served, and so will themselves present little problem. But some microbes produce toxins which remain even after the microbes have expired. Most such are proteins which are themselves destroyed by the heat of cooking; but some of these cannot be destroyed by cooking -- as for example botulinism toxin. In actual practice, most such heat resistant toxins are produced by anaerobic microbes which cannot survive in the presence of oxygen (eg, boulinism toxin). The combination of contact with the atmoshphere (ie, with oxygen) and cooking heat disposes of nearly all such problems. As in all cases with frozen food (crock pots are not unique in this regard), one safeguard is to defrost frozen ingredients at low temperatures at which microbes don't do well (ie, in the refrigerator), or to defrost them more quickly (eg, in a microwave or a conventional oven), before putting them into the crock pot.
Perpetual stews should not be left in the crock as the crock cools very slowly.
Warning: Because these cookers are portable/movable, contain large quantities of hot food and water, and because they are left unattended during long cooking times, they are dangerous around small children and exploratory pets. Cooking areas should be blocked off -- effectively -- if either might be present unattended.
A check of Usenet and News articles failed to find one article in which a crockpot started a fire. A minority seem to be frightened that the crockpot will cause a fire when they are not looking. The majority of responses point out that crockpots are designed for long hours of unattended cooking, that they leave appliances on all the time without incident, and that they have never had a problem with their crockpot. Many users report that burning food is nearly impossible as overcooking a stew merely turns it to an edible mush. The most likely source of a fire using a crockpot would be a shorting of the cord (a hazard with any electrical appliance that can be avoided using the right fuses and/or circuit breakers, not keeping mice or animals which chew cords in the kitchen and not testing out knives on said cord). Any issues with the heat may be dealt with by isolating the appliance from surrounding flammables on a large metal plate or stone surface.