“Discovery” covers all the methods used to get at all the relevant facts in a dispute with a creditor about the discharge of a debt.
If you object to a creditor’s proof of claim in your Chapter 13 case, and prevail in that dispute, you pay nothing on that debt.
In most straightforward Chapter 7 cases all debts not secured by any collateral are discharged–forever written off. You pay nothing on them.
Your debts can be “secured,” “priority,” or “general unsecured.” How bankruptcy treats your debts depends on which kind they are.