Final answer:
A cosigner is a secondary obligor who legally pledges to repay some or all of the money on a loan if the original borrower does not fulfill the duties. They provide a guarantee that the obligations will be discharged in case of default.
Step-by-step explanation:
A cosigner is another person or firm who legally pledges to repay some or all of the money on a loan if the original borrower does not fulfill the duties. They act as a secondary obligor by assuming the liabilities of the original party to the agreement.
For example, if a student applies for a loan to finance their education, they may need a cosigner, such as a parent or guardian, who promises to repay the loan if the student is unable to do so. In this case, the cosigner is the secondary obligor.
By cosigning, the external party (cosigner) ensures the repayment of the loan, acting as a guarantee for the lender in case the original borrower fails to fulfill their obligations.