Two main things can keep your policy active: premium payments and cash value balance (also known as the policy fund).
Premium payments: You typically need to pay your premiums on time. However, universal life allows you to have flexibility with your payments as long as the policy stays funded.
Cash value balance (policy fund): The policy stays active as long as there's enough money in the cash value account to cover the cost of insurance charges.
With universal life insurance, you have more control. You can skip a payment if you have enough cash value built up, or you can make extra payments to keep the balance healthy. But if both your premium payments stop and your cash value runs out, the policy ends.