Pressure Cookers are generally made of Aluminium or Stainless Steel. Food is cooked much faster by pressure cooking than by other methods (except perhaps microwaves), and with much less water than boiling, so dishes can be ready sooner. Less energy is required than when boiling, steaming or oven cooking. Since less water is necessary, the food comes to cooking temperature faster.
The food is cooked at a temperature above the normal boiling point of water, killing bacteria and viruses. The pressure cooker can also be used as an effective sterilizer, for jam pots and glass baby bottles for example, or for water while camping. With pressure cooking, heat is very evenly, deeply, and quickly distributed.
It is not necessary to immerse food in water in a pressure cooker. Enough water to keep the pressure cooker filled with steam is sufficient. Because of this, vitamins and minerals are not leached (dissolved) away by water.