PUBERTY

The age of puberty for girls is 10-12 years and for boys 13-14. The age at which male and females  are " sexually mature" is known as puberty. At puberty the reproductive organs attain maturity and therefore produce gametes, as well as hormones. 

Menstrual cycle

It is the cyclic activity manifested by the uterine wall of primates only, resulting in bleeding or menstruation. Bleeding is caused due to the breakdown of the innermost wall of uterus (endometrium), causing the underlying blood vessels to rupture. It lasts for 28 days . The breakdown or removal of inner, thick and soft lining of the uterus along with the blood and mucus, in the form of vaginal bleeding is called menstruation.

Sub primates also show cyclic activity in females. It is known as estrous cycle.