Realtors and appraisers are both professionals who are asked to estimate the value of their real estate. The appraiser depends on specific and verifiable comparable sales. They must consider many factors such as condition, age, square footage, location and site size. The appraiser must provide a defensible and carefully documented opinion of value. The realtor will list properties that are active listings and sold properties. They do not make any adjustments for the differences between the subject and the comparable sales and listings.
The realtor is giving a range of values without providing any adjustments between these features. The appraiser must adjust for all differences between these sales and listings and be able to defend it for the bank or in court.
Real Estate Appraisers typically have taken many hours of courses to be able to make these adjustments and have a document which is supportable for their clients. Appraisers are required to take continuing education every 2 years to maintain their license.