As the name implies, the average score is the final score obtained by adding up the scores of all students in the class and then dividing the total by the total number of students.

Variance is to find the average of the sum of all numbers (that is, the above), then subtract their average from each number, the square of the difference of each number, add it up, and finally divide it by the weight (that is, divide it by how many numbers there are).