What is puberty?

pu·ber·ty

noun
"The period during which adolescents reach sexual maturity and become capable of reproduction."

synonyms: adolescence, pubescence, sexual maturity, growing up;

"Girls get a head start on puberty — and growing taller — because they usually start these changes between the ages of 8 and 13. Most boys, on the other hand, don't begin until between the ages of 9 and 14. So that's why girls are often taller than boys during that time."