For example, a level term life insurance policy has level premiums each year for the entire length of time you are insured.
So, if you buy a 15 year level term policy with an annual premium of $300 you would pay $300 one time each year for a period of 15 years.
Your life insurance premiums stay the same each year for the duration of your "term" with a level term life policy.
The longer your term, the longer your premiums stay the same.
However, if you are alive when your term policy expires (at the end of the 15 year period in the example above), and you want to continue coverage, you may be able to "renew" your policy for another "term" with a duration of 10 years, usually.
But, your annual premium will be higher because it will be based on your age at the time you renew your term life insurance policy.