Where a fracture would be the bone completely broken, a chip is just a little chunk of the bone breaking off, leaving it floating around within the body. Sometimes a chip will require surgery to remove it if it's in a bad location, other times vets opt to leave it alone.
I heard something about a piece of bone separated but not broken...
but I don’t understand what does this mean?
Personally I know it as a piece of the hoof that gets broken off.