In Chapter 7 bankruptcy, if you owe money on any debts that are secured by personal property, such as a car or furniture, you must file a statement of intention as to what you plan to do with that personal property. You have three choices: surrender the property, redeem the property (pay the debt off in full satisfaction), or reaffirm the debt.
When you reaffirm a debt, you are creating a new contract with a creditor which will not be discharged in bankruptcy. That means that if, after your bankruptcy is discharged, you default on the new agreement, the creditor can sue you, repossess the property, and garnish your wages or bank account.
A creditor cannot force you to sign a reaffirmation agreement. However, the consequence may be that you will have to surrender whatever property the loan with creditor is secured by.
Signing a reaffirmation agreement is a big decision. You should talk about whether doing so is a good idea with a bankruptcy lawyer.