Poultry is a term used to describe domesticated birds raised for food. In the United States this means mainly chicken and turkey. Game hens are another form of poultry that can be found in some supermarkets. Duck, although common in Europe and Asia, appears more often on restaurant menus than in your average American grocery store.
Most supermarkets offer organic, free-range, and natural birds. Freerange chickens have more flavor because they are allowed to exercise a bit more. Natural birds contain nothing synthetic, no preservatives or artificial flavoring or colorings, but standards permit antibiotics and hormone use. Organic birds are fed grains that have not been exposed to chemicals and pesticides. They may not be treated with antibiotics or drugs, and must be allowed to go outside and exercise.
Whenever possible, buy free-range, organic poultry. Common chickens are raised with profit, not health, in mind. They must be fed antibiotics to fend off disease. They are given growth hormones, which, coupled with lack of exercise, makes them so fat they cannot move. In addition, the food they are fed is grown with artificial fertilizers and chemical pesticides.
Kosher chickens are organic and free-range, and are processed under the strict supervision of a rabbi. They are also soaked in salty brine, which gives them a unique flavor.
When shopping for chickens, frugal cooks know that whole chickens are always less expensive than cut-up parts. But unless you possess good butchering skills, it can be worth paying a little more. Keep in mind that chicken fat occurs in and around the skin, which is easy to remove.