The bone is an item dropped by the skeleton.
Two to three bones are dropped by the bone block when mined.
Skeletons drop 0-2 bones upon death.
A bone can be used to craft three pieces of bone meal.
Four bones can be used to craft a bone block.
Five bones can be used to craft eight bone shurikens.
Bones can be used to tame wolves by shift-clicking onto them, but it will take more than one bone to tame the wolf.