Answer:
Purpose: to impart better night vision to nocturnal animals by increasing the available light for photoreceptors.
It is called "tapetum lucidum".
Step-by-step explanation:
The reflective material in the choroid coat of some nocturnal vertebrates is called "tapetum lucidum". Its function is to improve the night vision of nocturnal animals. The tapetum lucidum serves to reflect the dim light available in the night. The reflected light re-stimulates the photoreceptor cells present in the retina. This increases the available light for night vision.
Tapetum lucidum makes the eyes of nocturnal mammals to shine at night.