There are three types of appraisals that can be done, but only one by a Realtor.
The highest appraisal will be given if it is for a refinancing of the property.
The lowest appraisal will be given if it is for taking out a mortgage on the property.
A Realtor can give you a current market evaluation based upon the comparison of your property to very recent sales in the immediate area.
A Realtor's market analysis is free of charge, but much more information is needed.
Want to know what your property is worth? What is the address? What is the interior square footage? Is it a multi-use property, storefront, office building? Is it rented? Who are the tenants, how long are the leases, how much rent are they paying, what are the yearly escalations on the rent, are the leases single, double or triple net leases?
There are more questions that would be asked. I hope this provides you with some understanding of what is involved.