Perhaps rather basic, but for those individuals that need the details of an appraisal, David Goldstein outlines what exactly is an appraisal, the ingredients of the appraisal, and the difference between a Cost Approach and Sales Comparison Approach, and in some circumstance (commercial properties), the Income Approach.  The full article may be viewed at: http://www.realestatearticledirectory.com/articles/appriasal-and-home-evaluation/article1250.html