If your life insurance policy expires because it has reached the end of contract period and there is no option for renewal of your coverage, the policy ends and you have no more life insurance.
For example, term life insurance policies usually expire at a specified age. You usually have an option to convert your term life policy into a permanent life insurance policy sometime before the expiration date on your term policy. Usually, term life policies offer coverage for up to 30 years, or until a certain age, like 65 or 70.
If you mean by expiring going out of force because of non-payment of your premiums, if you are healthy you can often re-instate your life insurance policy by paying all of the back premiums owed.
Some life insurance policies have a cash value inside the policy (permanent life insurance) that is paid to the owner of the life insurance contract when the policy expires or matures.