Generally, the mean of a set of values is a value that represents the average or middle of the values. There are many ways of calculating such a value, the most common being the arithmetic mean and the geometric mean.
In a dataset or frequency distribution, the arithmetic mean is one measure of central tendency, that is, it is one way of defining the center of the data, the value about which the data is approximately evenly distributed. It is a useful measure of central tendency if the data has a uniform or symmetric distribution. However, it can be misleading if the data is strongly skewed. The classic example: If Bill Gates walks into a homeless shelter then everyone in the building is rich—on average.