What is debt snowball? Dos it require creditor approval?

Answering your queries one by one.
The debt snowball is a debt relief method where you list all your debts from the lowest outstanding balance to the highest. Then, make minimum payments on all your unsecured debts and pay a little extra on the debt with the lowest balance. Once you repay this debt in full, follow the same strategy with the next lowest balance debt in your list. Continue with this until you pay off all your debts.
Yes, you can do it on your own.
No, you don't require any creditor approval since it's your own debt repayment strategy. You don't have to negotiate anything with your creditors.
Check out: https://www.debtconsolidationcare.com/financial-infographics/snowball-avalanche.html

The best part of the debt snowball method is that it helps you pay off small debts fast. It gives you motivation to pay off other debts one by one. You learn the art of managing money efficiently by focusing on one debt at a time and taking care of other debts as well.

No, it doesn't require the creditor's approval.

Debt snowball method is a good way to repay the multiple unsecured debts. Since it is a DIY method, you don't need to take approval from your creditors.

No, you don't require any creditor approval, you can do it on your own. But you have to maintain discipline while following this debt repayment strategy.