Mineralization is a process in which a biological organism produces an inorganic substance. In this case, you are likely referring to the production of new bone material. Bones are produced by cells called osteoblasts. They utilize calcium and phosphate ions to precipitate new inorganic bone material.
Vitamin D is a group of fat-soluble chemicals that are similar to the steroid family of molecules. It is not technically a vitamin in that the body can produce it from an internal chemical reaction in the skin involving sunlight, but it is nonetheless an important part of the human diet. Members of the vitamin D family help the body to more effectively absorb calcium and phosphate ions through the small intestine to enter the bloodstream. They can then be used by osteoblasts for mineralization. Lack if vitamin D can produce a condition called rickets, where a person has soft or weakened bones.