A private loan is a non-governmental loan made from a bank to an individual for the purposes of covering the unpaid portion or "gap" in your cost of attendance, which includes housing, tuition, food, travel, books, etc... Your "gap" can be defined as any expense not covered by scholarships or other aid offered by your college.
The Parent Loan for Undergraduate Students, or PLUS, is a federally backed student loan that parents can take out on behalf of their undergraduate children to pay for educational costs. PLUS loans have fixed low-interest rates that do not inflate with economic changes.
GradPLUS Loans are federally backed student loans specifically for graduate students. These loans have fixed interest rates for the entire life of the loan. The interest rate is standard for all borrowers and not based on credit strength.