What is the whole controversy of the Bell Curve Theory in Psychology about?
If you’re talking statistically, if people are being compared on some trait (say test scores) the majority of them will receive scores close to the mean (average) score. You will have some people above the mean and some below. The point of the bell curve shows that there are usually people closer to average and the farther away you get from the average are the people who scored substantially higher or lower than the people who are closer to the mean. It takes on a “bell shape.” I don’t know about any controversy about it per se, but that’s just what the bell curve is.