Mortgages can be defined as either government-backed or conventional. Government agencies like the Federal Housing Administration (FHA) and the Department of Veterans Affairs (VA) insure home loans, which are made by private lenders. This insurance is paid for by fees collected from mortgage borrowers. The US Department of Agriculture (USDA) loans money to lower-income borrowers through its Direct Housing Program. It also guarantees loans made by private lenders through its Guaranteed Housing Loans program. This backing is paid for by borrowers.
Mortgages not guaranteed or insured by these agencies are known as conventional home loans. They include:
About half of all conventional loans are called "conforming" mortgages, because they conform to guidelines established by Fannie Mae and Freddie Mac. These two government-sponsored enterprises (GSEs) buy mortgages from lenders and sell them to investors. Their purpose is to make mortgages more widely available. All conforming mortgages are also conventional mortgages.
Loans that do not conform to GSE guidelines are referred to as "non-conforming" home loans. Non-conforming loans that are larger than loan limits set by the GSEs are often referred to as "jumbo" mortgages. All non-conforming mortgages are also conventional mortgages.
Conventional loans held by mortgage lenders on their own books are called "portfolio" loans. Because lenders can set their own guidelines for these loans and do not sell them to investors, these products may have features that other mortgages do not. For example, a portfolio lender might allow a borrower to use investments like stocks and bonds as security for a mortgage for which she would not otherwise qualify.
Conventional home loans marketed to borrowers with low credit scores are called sub-prime mortgages. They typically come with high interest rates and fees. The government has created special rules covering the sale of such products, but they are not government-backed -- they are conventional loans.