A co-signer is normally a person you know, as in a member of your family or close friend that is agreeable to share the liability for making loan payments if you are unable to make the payments. Usually a parent will co-sign for their child that has no credit history yet or a bad credit score. When starting out in adult life this can be a good method to begin establishing your credit history. Also, the co-signers good credit might aid someone with poor credit to get accepted for a loan that they would be denied otherwise.