Before explaining health insurance policy, it seems pertinent to define what is health insurance?
Health insures is a specified policy that pays specified sums for medical treatment when an insurer is sick. Different insurance companies have different coverage variation in their policy. The causes of sickness may be:
Accident
Failure of any body organ
Injury
Sudden death due to organ failure or accidents
Disability
There are several other causes of sickness and death that a person may encounter. But their coverage varies from insurance company to company.

Accidents:
Very common policy, if a person is insured and come across an accident, he or she will be paid specified sum of money for his or her treatments and medication.

Failure of any body organ:
Failure of body organ is rarely paid as organs can not be purchased. However, under this policy, the patient is given huge sum of money to repair and make use of the same organ. For further information you can visit your area health insurance companies and ask them what their policies against organs failures are.

Injury:
The causes of injury most often may be accidents. In this case, you will also fund for your treatments.

Disability and Disable Children:
Due to accident or any sickness, you become disabled; you will be given specified sum of money.

Sudden Death:
When purchase your health insurance, it will be mentioned in statement, how much will be payable in case of a person gets died.

These all are simplified policy; there are other conditions and policy that varies greatly between companies to companies.