An automated valuation model (AVM) is a computer-driven formula that uses basic property details (beds, baths, square feet) and recent comparable sales to deliver a home value estimate.
An appraisal is an in-person valuation of a property by a state-licensed appraiser. The appraisal value is determined by hand-selected comparable sales, and a visual inspection of the property and its neighborhood.
AVMs are fast and free, while appraisals are expensive and can take days (or weeks) to finish. You can get a pre-listing appraisal before setting a list price on your home.