What is puberty? What is it caused by? What changes occur in boys and girls during puberty?

Puberty is the time of life when a boy or a girl becomes sexually mature. It happens at the age group of 10–15 for girls and 11–16 for boys.
Puberty is caused by the release of hormones.
Changes that occur in boys during puberty:
(i) Deepening of voice
(ii) Growth of facial hair (beard and moustaches)
(iii) Development of muscles and broadening of shoulders
(iv) Production of sperms by the testes

Changes that occur in girls during puberty:
(i) Development of breast
(ii) Widening of pelvic region and broadening of hips
(iii) Start of menstrual cycle