Automatic renewal allows you to keep enjoying the Mario Kart Tour Gold Pass service by automatically renewing your subscription each month when the one-month validity period ends. This allows you to keep using the same Gold Pass.
If you do not wish to continue your subscription, you must cancel automatic renewal at any point during the free trial period. Then, you will not be charged at the end of the free trial period.
Both during the free trial period and during a paid subscription period, if you do not cancel automatic renewal before the Gold Pass term of validity ends, your Gold Pass will automatically be renewed, and on an ongoing basis until you cancel it.
Check here for how to cancel automatic renewal: How do I cancel automatic renewal?