Puberty means something like "sexual maturation". All people go through the period of puberty. It is a normal part of growing up, like the growth of bones. Puberty almost always begins at the earliest when a child is nine years old. Once sexual maturity is reached, men can have children and women can have children.
Puberty occurs when the body produces more of certain hormones and releases them into the blood. These hormones are called female sex hormones in girls and women and male sex hormones in boys and men.
Puberty does not happen evenly. At different times, the body undergoes completely different changes. The skin can also change: Many people have problems with pimples during this time, maybe even downright acne.