Slow cookers are appliances that work with very low temperatures and cook meals over a long period of time. They cook meals unattended and work electrically through a controlled heating element.
Pro: Time Savings
The most obvious advantage of a slow cooker is that meals can be turned on before you leave home for work and the meal will cook while you're out. You don't need to be around to prepare or add anything.
Slow cookers are low tech, so anybody can use them. They don't need to be programmed, and most cookers contain only a couple of switches: one to choose the amount of hours to cook for (usually one to eight) and one to choose temperature (low, warm, high).
Pro: Low-Fat Cooking
Meals cooked with a crock pot are healthier, as the food steams in its own liquids and you won't need to add oils or fats.
Con: High Price
Crock pots are not cheap--even the simplest models can cost over £65. This is substantial initial investment, especially because most modern appliances can be had today for a quarter of that price.
Con: Limited Use
Crock pots are not particularly helpful unless you're a meat eater. Though you can cook potatoes, chilli and curries in a slow cooker, herbs and vegetables may lose their flavour after cooking for so long. Meats, on the other hand, will benefit from slow cooking.