PMI stands for Private Mortgage Insurance or Private Mortgage Insuror. Privately-owned companies provide this mortgage insurance. They offer both standard and special affordable programs for borrowers. These companies provide guidelines to lenders that detail the types of loans they will insure. Lenders use these guidelines to determine borrower eligibility. PMI's usually have stricter qualifying ratios and larger down payment requirements than the FHA, but their premiums are often lower and they insure loans that exceed the FHA limit.