There are 2 types of sexual characteristics in human beings: Primary Sexual characteristics and Secondary sexual characteristics.
(a) The sexual characteristics which are present at birth are called primary sexual characteristics. They include internal and external sex organs which are present in babies at the time of their birth. The primary sexual characteristics in males are testes, penis, seminal vesicles. The primary sexual characteristics in females are ovaries, oviduct, uterus, vagina etc. They are directly involved in reproduction.
(b) The sexual characteristics controlled by hormones which distinguish between sexually mature males and female but are not directly involved in reproduction are called secondary sexual characteristics.
In secondary sexual characteristics, the body parts develop special features which make it easier to distinguish a boy and a girl. The secondary sexual characteristics in males are:
(1) Hairs grow on the face in the form of beard and moustache.
(2) Shoulders and chest broaden.
(3) A deeper voice or low pitched voice.
In females, visible secondary sex characteristics include pubic hair, enlarged breasts and widened hips of females.