Sale Price is the factual amount paid by a buyer for a property or group of properties.
Appraisal is a detailed single-property estimate of value, obtained for purposes such as a mortgage, determination to sell, home equity loan, or estate valuation.
Assessment is a mass appraisal of property as of January 1 of the year of reassessment (odd years for real estate assessments, annually for personal property assessments) and is for tax purposes. The process involves valuing a group of properties as of a given date, using standard methods, employing common data, and allowing for statistical testing.