An appraisal is a licensed appraiser's written opinion of a house's value, based on its condition and recent sales of similar houses nearby. A lender orders one to confirm the house is worth what it is financing before approving the loan. The appraiser works for the lender, not the buyer or the seller, even though the buyer usually pays the fee.
Why it matters
If the appraisal comes in below the agreed price, the buyer's loan may not cover the gap and the deal can stall.