Regression to the mean is a statistical phenomenon where extreme values of a variable tend to move closer to the mean or average of the data set over time. It is often used to explain why extreme events are often followed by more average events. This phenomenon can be observed in many different areas
In statistics, regression toward the mean is the phenomenon where if one sample of a random variable is extreme, the next sampling of the same random variable is likely to be closer to its mean. Furthermore, when many random variables are sampled and the most extreme results are intentionally picked out, it refers to the fact that a second sampling of these picked-out variables will result in "less extreme" results, closer to the initial mean of all of the variables.