I had a similar issue a few years back. I ran across a website that gave me way more information than I needed. Here are the basics of what it contained.
Broilers: Chickens 6-8 weeks old and weighing about 2 1/2 pounds
Fryers: Chickens 6-8 weeks old and weighing 2 1/2 - 3 1/2 pounds
Roasters: Chickens less than 8 months old and weighing 3 1/2 - 5 pounds
Broilers, fryers, and roasters can generally be used interchangeably based on how much meat you think you'll need. They are young chickens raised only for their meat, so they are fine to use for any preparation from poaching to roasting. You may need to adjust cooking times or amounts of other ingredients (like stuffing) based on what the recipe called for and the size of your chicken.
Stewing Chickens: Chickens (usually hens) over 10 months old and weighing 5 - 7 pounds.
Stewing chickens are usually laying hens that have passed their prime. They are older and their meat is usually tougher and more stringy. This type of chicken is best used in stews (as the name implies!) where the meat has time to break down during the long, moist cooking.
From my experience (bbq & smoking) the fryers cook evenly and with the best ratio of meat to cook time.
