If a conventional loan falls within Fannie Mae's and Freddie Mac's loan limits, it is referred to as a Conforming Loan. If the loan amount exceeds the maximum permissible loan amount of these two agencies, it is called a JUMBO, or Non-Conforming Loan.
Conventional lenders typically insist that the borrower put down more than 20% on a JUMBO loan. Interest rates on JUMBO loans generally run between 3/8% to 1/2% higher than Conforming Loans. The difference in the interest rate between Conforming and JUMBO loans is higher when mortgage money is not plentiful. The difference typically decreases with the abundance of mortgage money.