A co-signer takes full responsibility for paying back a loan, along with the primary borrower.
Often a co-signer will be a family member. The co-signer is obligated to pay any missed payments and even the full amount of the loan if the borrower doesn’t pay. The co-signer’s credit also can be harmed if the borrower is late making payments.
Having a co-signer on your loan gives your lender additional assurance that the loan will be repaid.