Yield spread premium is defined as:

Yield spread premium refers to the additional income that a lender may pay to a mortgage broker or another third-party originator when the interest rate on a loan is set higher than the lowest available rate, often described as "par." This premium is essentially a way for lenders to incentivize brokers to offer loans at higher rates, which can ultimately expand the lender's margin on the loan.

When a borrower locks in their interest rate, if it is above par, it creates a situation where the lender gains more from the interest payments over time. The broker benefits from receiving a yield spread premium as compensation for facilitating this arrangement. This concept is integral to understanding how pricing and commissions in mortgage transactions work, as it illustrates the dynamics between borrowers, lenders, and brokers in the loan origination process.