What is a "soup chicken" How is "soup chicken" different from "cooking chicken". Is it a different breed or just old chicken? Can I eat its meat?

I have always made soup from the bones of boneless chicken I cook. Today I got a chicken specifically for soup, whose packing said "ideal for broth". So I broke its bones and put the entire thing to boil for an hour. Now my normal chicken's flesh just fells apart after boiling for an hour. This one was still firm and a bit hard and leathery. It was actually hard to remove the flesh from the bone after all this boiling. And the flesh itself was kinda unappetizing. I still cut it up in cubes and put it in the soup(because, protein!).

So is it a different kind of chicken, or just old chicken (I know the meat of old cows becomes leathery). Is it safe to eat the meat?
You've already guessed it correctly, soup chickens are basically old codgers that are too tough to roast or fry up. They may get tender enough to eat if you cook them slow for 2-3 hours but often even that won't make them palatable. The only reason I'd ever use them is if I wanted to make loads of chicken stock and didn't plan to use the meat.