To understand how a pressure cooker works, you need to know just a little about physics. to put it simply, water boils at 212o Farenheit. At this point, no matter how long you continue to boil, it always stays the same temperature. As the water evaporates and becomes steam it is also the same temperature, 212o F.
Pressure cookers are especially designed cookware of aluminum or stainless steel. All models have a lock-on lid and a vent or pressure relief valve. Most pressure cookers are designed to be used on top of your stove, but there are some electrical models and also a one that is supposed to work in the microwave.