A reaffirmation agreement is an agreement between the debtor and a creditor by which a debtor becomes legally obligated to pay all or a portion of an otherwise dischargeable debt. What that means is that, if you sign a reaffirmation agreement, and you become unable to pay that debt, the creditor will be able to sue you to collect the debt. That debt will not be eliminated by your bankruptcy.
Such an agreement should be filed within 45 days after the first date set for the meeting of creditors. A debtor who signs a reaffirmation agreement has 60 days after the agreement is filed, or until the discharge date, whichever occurs later, to change his mind and inform the creditor that the agreement is rescinded. Debtors entering into a reaffirmation agreement without counsel representing them will need to attend a hearing before a judge to determine if the agreement will be valid.
A reaffirmation agreement greatly affects your rights in a bankruptcy, and you should consider discussing any such agreement with an attorney before you sign one.