The periosteum is made up of a thin, dense membrane that contains nerves and blood vessels.
The Compact Bone is smooth and very hard. This is the part of the bone that is shown when you look at a skeleton.
The Cancellous Layers looks like a sponge. This part of the bone is not quite as hard as compact bone, but it is still very strong.
The bone marrow is a sort of thick jelly that makes blood cells.