An appraiser will dertermine what is called the "market value" of your home. It is not only what your home is worth, but what an average buyer would be willing to pay for it in your real estate market.

The accuracy of assessed values varies greatly in different areas. The county assessed values are actually accurate sometimes, but more often are low.

With the assessed value of your home usually being lower than the market value of your home, this is a good thing. Your home's property taxes are based off of the assessed value of your home and not the market value. Therefore, by having your taxes calculated off of the assessed value this will help most homeowners to benefit from cheaper property taxes. Some very commmon questions from consumers are:
"Will my taxes go up if my house appraises for more money?"
"If I refinance my home for more money than I bought it for will my property taxes increase?"
"Will the lender provide a copy of the appraisal to my county auditor?"
"Will the auditor be able to find out how much my house appraised for?"
The simple answer to all of the above questions is no. Your county auditor will not reassess your property taxes based on how much you owe on your mortgage or how much your house appraises for. Most county auditor departments do their own property value assessment and this is how they come up with the value of your property. The auditor will never see a copy of your home's appraisal when you refinance and your lender will never provide the county auditor a copy of the appraisal report either. Therefore, the assessed value of your home is what is used to determine your property taxes and the market value/actual value is how much your home is worth on paper and could possibly sell for.