You know your stock is good when it turns to gelatin in the fridge. Here, I'm spooning out borsch to reheat: it stays in a lump on the spoon.
Broth is made with meat only, whereas stock includes the bones. And long, slow cooking with a little vinegar ensures that all the good stuff is extracted from the bones. My Amish butcher told me they simmer their beef stock for days and when it's done, the dogs aren't even interested in the scraps and bones. Here's a short article that explains why homemade stock is so good and so different from commercial junk.
I encourage you to make stock: it's thrifty, nutritious, and simple to do. And really delicious.
1. get chicken backs/wings/necks or beef bones
2. roast them for an hour or so at low heat (this gives better color and flavor, but you can skip this step)
3. put the bones in a pot with water to cover, a few unskinned onions and some other savory vegetables; a few peppercorns, some salt, and about 1/4 c. vinegar for a big stock pot
4. simmer for at least 12 hours and up to 3 days
5. strain, skim the fat if you wish, and package in several sizes; refrigerate for up to a week or freeze it