Brandy: Most of the answers below are correct, but I wanted to get a little more detailed for you. When an appraisal is done for a purchase, the appraiser comes out, measures the home to determine the square footage and also comes into the house to determine the overall general condition as well as the number of bedrooms, baths, and other rooms. They then compare this to the sales of other properties that are similar (comparables) that have sold recently to determine what the current value of the particular home being sold is.
In the tax appraisal, as someone else mentioned, in NC they are done only once every 4 to 8 years, are usually only a driveby to see if there are any apparent changes to the home, as well as checking for any improvements done since the last tax appraisal that building permits were issued for. Typically in a tax appraisal increases (or decreases) in value are not usually made to an individual home, but are done by a particular area. For example, if you live in a rather large subdivision, they may determine what the change in the average value in the subdivison is, based on recent sales in the subdivision, and increase or decrease the value on all homes in the subdivision by that figure. An individual property may also be adjusted based on any improvements (other than cosmetic) since the last appraisal.
In short, the real estate purchase appraisal is a determination of the value on the particular date that the appraisal is completed. The tax appraisal, depending on when it was last done, may or may not be an accurate value of the home at any given time. In Henderson County where you live, the last tax appraisal was done in 2010, and effective in the tax year 2011, so may not accurately reflect the value today.