A permanent life insurance policy never expires, it stays "In Force" for your entire lifetime, as long as you pay your premiums on time.
A term life insurance policy expires when your "term" ends.
So, if you buy a 15 year term life policy, your life insurance coverage expires fifteen years from the day you started your policy.
If you pass away before the expiration date of your life insurance, the death benefit is paid out.
If you are alive when the term life policy expires, there is no payout on your term insurance, your coverage just ends.
Learn more about how term life insurance and permanent life insurance works.