Bone meal is just that, ground up sterilised bones.
Add fish, and blood and you get the second.
Pure bone meal is a slow release food for plants.
B,F and B gives an instant boost to plants as the blood and fish are more soluble so can be taken up immediately.

Bonemeal is high in phosphorus which is beneficial for the roots of plants, including root vegetables and bulbs, and for fruits. FBB is nitrogen rich so promotes leaf growth.

Or my personal explanation is this - bonemeal takes years and years and years to break down and as far as I'm concerned, is a waste of money - its a by product that industry is glad to get rid of. However, it may be of some use over a decade or so in the bottom of planting holes for its phosphorus content and can be used year round. Fish, blood and bone is a fertiliser that provides, roughly, a balanced NPK similar to that of Growmore, and is what I use in the bottom of planting holes in spring and early summer. I would not recommend either for use as a top dressing, even if you rake it in - animals of all sorts love it and you'll find dogs, cats, foxes and lord knows what else ferretting about trying to eat it....

BAMBOO is absolutely right, as we are infested with foxes. I have stopped using it for this reason.