The nails start to develop from the pocket beneath the skin, which is known as “matrix” that continuously produces new cells. The newly grown cells push the old cells to get packed together. The old cells become firm and flatten, basically becoming the keratin. Then, they are finally pushed up through the fingertips.
You may also have heard about cuticle, which is a place where the nail meets the skin. It protects the nail from the germs and damages as it grows out of the finger. The half-moon shaped whitish lunula is a part of the matrix that you normally see at the bottom of nails. If you can’t see it, don’t worry, because it can be under the skin.