USPAP (Uniform Standards of Professional Appraisal Practice) is the set of rules, standards, and guidelines that state certified and licensed appraisers are required to adhere to when performing professional services as an 'appraiser'. USPAP is published, maintained, and updated by the ASB (Appraisal Standards Board) of the Appraisal Foundation, which is a pseudo-governmental agency charged by the US Congress with promulgating appraisal practice standards.
Pronounced 'USE-pap', the actual 'document' includes 10 'Standards', 32 'Advisory Opinions', and 293 'FAQ's'. The Standards cover all general fields of appraisal, including real property, mass, personal property, business, and review appraisal guidelines. Included in the Standards is guidance on the development, reporting, and recordkeeping requirements set forth by the ASB. The Advisory Opinions can be thought of as elaborations on the various standards and offer detailed guidance along with example scenarios of the application of the different standards. The FAQ's can be thought of as the ASB's 'interpretation' of the various standards and are used by appraisers for clarification of different aspects of the Standards.
An online version of the Standards can be accessed via this hotlink: http://www.uspap.org/