say if there were the following numbers: 1,2,2,2,3,4,5 so you
would add them all together which is 19 and then divide 19 by how
many numbers there are which is 19 divided by 7= whatever

The mean is usually the arithmetic mean - there are other means in maths. For a set of numbers, the arithmetic mean is the sum of the numbers divided by the number of numbers.