Theaverage is simply the average of a set of numbers. The standard deviation is a measure of how spread out the numbers are with respect to the average. ~64% of the numbers will be within 1 standard deviation of the average.
The mean (or average) is just an average over your sample of numbers, such as (n1+n2+n3)/3. The average does not have to be a number in your sample set, but does have to be in between your sample.
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