Short answers, pulled from the story.
There are 206 bones in the adult human skeleton. The exact number depends on counting choices, such as whether the pelvic bones on each side are counted as one or three, and whether the coccyx is one bone or four. A newborn has over 270 bones, some of which fuse together as the body develops.
There are several types of skeletons, including the exoskeleton, a rigid outer shell that holds up an organism's shape, the endoskeleton, a rigid internal frame to which organs and soft tissues attach, and the hydroskeleton, a flexible internal structure supported by the hydrostatic pressure of body fluids. Skeletons can also be classified by rigidity, with pliant skeletons being more elastic than rigid ones.
An exoskeleton covers the outside of an animal's body and serves as armor against predators, as in arthropods and molluscs. An endoskeleton is an internal support structure made of mineralized tissues, found in chordates, echinoderms, and sponges. Arthropods with exoskeletons tend to be relatively small on land because an external skeleton can be heavy relative to the animal's mass.
The skeletons of birds are adapted for flight, with hollow, lightweight bones that reduce the metabolic cost of flying. Their bones are shaped to endure the stress of flight, with a round and thin humeral shaft and skeletal elements fused into single ossifications, which gives birds fewer bones than other terrestrial vertebrates. Birds also lack teeth and a true jaw, having evolved a lighter beak.
A hydrostatic skeleton is a flexible cavity within an animal that provides structure through fluid pressure, and it is always internal. Hydrostatic skeletons occur in soft-bodied organisms including jellyfish, flatworms, nematodes, and earthworms. The walls of these cavities are made of muscle and connective tissue, and they transmit the forces of muscle contraction to allow movement.
The largest bone in the human body is the femur in the upper leg, and the smallest is the stapes bone in the middle ear. In an adult, the skeleton comprises around 13.1% of total body weight, and half of that weight is water. The human skeleton takes 20 years before it is fully developed.