Most people think that all or at least most of the bones in the human body are hard and tough. This whoever is only partially true.. most bones in the human body are indeed hard and tough but only that outer coating of bones is truly hard and tough, while the inside will usually remain soft.
Being part of the skeletal system means that the bones have the responsibility to give rigid support to a person's body. Despite being living and growing tissue bones are able to maintain a rigid space by turning their outer layer into compact bone. The compact bone has small canals running through its surface, these canals facilitate the passage of blood cells. So a human bone will have 2 general parts the outer compact bone and the inner spongy bone. Each bone will have a different ratio of spongy bone to compact bone but usually the compact bone will account for 4/5th of the total mass of a bones, however the general grouping of bone serves as a partial indicator of how much spongy bone to compact bone ratio it will have.
Bones in general may be grouped by their shape and outward appearance the major groupings for bones are as follows flat, short, long, and irregular. Flat bones will have thin layers of compact bone surrounding the spongy bone inside. Long bones are our stereotypical bone, like the bones in the legs and arms are long bones. Short bones would consist of the many many connection bones like those found in a person's feet and hands. While as the name implies irregular bones are just grouped together because they dont have any other group.