Kindly explain me what is
mean
and what is zero mean
Mean is just average... it's the "normal average" if you will
When I was young, I was told it's what all those "mean" teachers do to figure out your grade
You sum up all of your values and then divide by the number of values that you have
A zero mean is a zero average, or equivalently, when you add up all your values, the sum is zero