In a Home Purchase, What Are Discount Points

In a home purchase, what are discount points?

A) A reduction in the annual interest rate of the mortgage loan because the buyer made a higher-than-required down payment
B) A reduced annual interest rate because of a very high credit score
C) Interest paid up front to the lender in return for a reduced annual interest rate
D) A reduction in the closing costs due to the fact the buyer put up a large amount of earnest money