When a collection agency is involved in the collection of an unpaid debt, the debtor sends one payment each month to the agency. The agency's gets a portion of this payment and the rest goes to the orginal creditor. The creditors are satisfied that the debtor is trying to straighten out their debts and that they are receiving a regular amount every month. The benefit to the debtor is that they now make only one payment each month at an amount that they can afford, and are no longer being bothered by creditors.
The information on this page is meant to provide a general overview of the law. The laws in your state and/or city may deviate significantly from those described here. If you have specific questions related to your situation you should speak with a local attorney.