As already said by Mrs. A2, bone broth is just broth made of bones, but this might also help - some supermarkets sell bones for stock in their meat department, butchers will save bones if asked, or you can do what I do and save bones from every time you cook something with bones in eg a chicken or meat joint. I have to watch the pennies quite strictly, and it's actually cheaper to buy meat with a bone in and get several meals from it. Freeze bones until you get enough for broth (doesn't take many - one whole chicken's worth is enough) pour on boiling water (cheaper to boil in a kettle that bring a pot to the boil on the cooker) then reduce heat to simmer. Put a lid on if you wish, to maximise heat economy, or leave the lid off to reduce the quantity of water. After a couple of hours on simmer, take the bones out and when cool enough to handle, pick any meat off and add to the stock.