According to Wikipedia, the head restraints are an automotive safety feature, attached or integrated into the top of each seat to limit the rearward movement of the adult occupant's head, relative to the torso, in a collision — to prevent or mitigate whiplash or injury to the cervical vertebrae.
BUT did you know that the headrest of car seats is deliberately kept detachable and sharp so that it could be used to break open the glass of the car in case of fire and emergency.
The car's glass are also easily breakable from the inside of the car. Very few people knows about it and thus can't save themselves in case of emergencies.
Please share it with as many people as possible to educate.