Some mortgage terms don’t look like they sound. For example, a “balloon mortgage” is a mortgage loan in which the monthly payments are not large enough to repay the loan by the end of the term. So at the end of the term, the remaining balance comes due in a single large payment. (Source: Loan One Real Estate & Mortgage Glossary)
This means the borrower needs to be aware what is going to happen at the end of the loan repayment term.