The way it is supposed to work is that all property within the taxing governmental unit (town, village, city, etc.) gets appraised, the total amount of the government budget is compared to the total appraised value, and a tax rate of so many dollars per $1000 of appraised value is set, so everybody pays a fair share.
It never seems to work that way in reality. The best method to use for valuation is full value of the property. So if your property is valued at $100,000 (the real market value), your taxes would be based on it's real value. The problems start when properties in specific areas raise or fall at a different rate than would be normal within the governmental unit. This happens a lot with lakefront property, which raises faster than the average residential property. People who have owned those properties find their taxes raising faster than the others, which may put them in a financial bind just because the live where they do. Of course, their property has increased a lot in value, but that doesn't help them until they sell it.
Of course, it always seems that your $100,000 property is assessed higher than the $250,000 property down the road. Then again, you are not the town supervisor's brother-in-law!