Permanent life insurance is intended to cover you for your entire life. Some types of permanent life insurance such as variable life and universal life may not because they are typically not 100% guaranteed to last your entire life. These types of policies are dependent on how well the cash value in your policy performs. Since the cash value is invested by the insurance company and is dependent on market conditions, these policies may not last as long as you need them.
Term life is guaranteed for a specific amount of time and does not contain a cash value feature. A 20 year term policy will provide the stated amount of insurance for 20 years. No more and no less. However, you can convert a term policy into a permanent policy within a specified time range. Check your policy for this option.
There are other features of both types of policies that may benefit you. The best way to decide on what type of life insurance you need to to sit down with a professional that can explain in detail all of your options. We can help you with this.