Stocks are used in a variety of dishes on this site, for the most part I just use stock powder and go from there, but when I boil chicken for certain recipes, that is the time to make a nice stock which is saved for later use.
Stock is the result of simmering bones, meat, skin, and fat along with carrot, celery, garlic, onion, and rosemary and thyme if desired. Making stock is not set in stone.
Consomme is stock that has been clarified, as stock will be cloudy, consomme is clear.
Basic Stock can be Chicken, Beef, Pork, and Seafood. The other ingredients are dead easy, 2 carrots unpeeled sliced into 1 inch pieces, 3-4 stalks of import celery chopped into 1 inch pieces then through the tops as well (for Thai celery use several bunches). 1 onion cut into quarters (no need to peel just cut off the root end), 1 head of garlic cut in half across the cloves (just take the whole head of garlic, cut it in half and throw it in pot, no need to peel these). 2-3 plum tomatoes cut in half. 1 tablespoon black peppercorns.
Simmer the meat, bones, skin for about an hour, then add the vegetables and spices, simmer for another 2 hours. Skim any foam or bits floating on the top. Strain this and you have stock. Could not be any easier.
Chicken carcasses are sold in Tesco and open markets for this very purpose, chop the large bones to expose the marrow. For pork and beef stock any bones will work. For seafood stock, save crab shells and shrimp heads, tails, and shells, you can freeze these until you have a good quantity, about a 1 kilo worth.
Basic Consomme is the clarified version of stock, meaning it is clear. This is very easy. Once you have the stock strained, return that to the pot on a low simmer and add 2-3 egg whites, lightly whipped and some lean ground meat. This will float on the top and will attract solids in the stock to it, leaving you a clear stock or broth. When the stock is clear, remove the floating egg whites and ground meat and pour through a strainer one more time. Allow to cool and refrigerate.