It's life insurance for a set number of years - usually 5, 10, 15, 20 or 30 years.
With level term life policies your premiums you pay for the life insurance protection remain the same for the entire length if time you have the life insurance coverage.
So, if you have a 10 year level term policy, your premium will not increase for the 10 years period - they will remain the same each year for 10 years.
However, if you outlive the 10 year period of coverage, your life insurance expires. But, you may be able to renew your term life policy for another 10 year term. If you do renew coverage, your premium will increase based on your age at the time of renewal.
That's why you want to choose the "term" for your term life policy that meets your life insurance needs now, and in the future. So, you can keep the low initial rate you purchase with your term life policy for as long as you may need life insurance coverage.