Final answer:
Additional collateral is a security measure requiring the borrower to pledge extra assets to secure a loan. This allows the lender to seize and sell those assets if the borrower defaults. Contrarily, a cosigner is someone who agrees to pay back the loan if the borrower cannot.
Step-by-step explanation:
When a lender requires additional security or collateral from the borrower, in addition to the property being mortgaged, it is an extra measure to ensure the loan will be repaid. This additional security could take the form of valuable assets like property or equipment. The practice of securing these additional assets is done to protect the lender, giving them the right to seize and sell these assets if the borrower fails to repay the loan. In contrast, a cosigner is another individual or entity that legally agrees to repay the loan if the original borrower defaults. It's also worth noting that lenders might require other forms of risk mitigation, such as copayments in insurance policies.