A formal written evaluation supplied by a professional, licensed property value estimator, the appraiser. The appraisal contains an estimate of a property's fair market value. The appraisal is based on the sale price of comparable homes in the area and the property's specific features. Lenders usually require an appraisal, before approving a loan, in order to have an accurate idea of the property's current value. A recent appraisal protects the lender from making a loan for an amount that is greater than the percentage of the home's value that the lender's requirements permit.