In machine learning, the standard deviation, what does it mean ( with in one standard deviation of the mean), how one?

Question

And what does it mean data is normally distributed?

Answer 1

Sumer Fattoum read this
https://www.varsitytutors.com/hotmath/hotmath_help/topics/normal-distribution-of-data

Answer 2

Ok, but the range here from - 1 till 1 is 2x the standard deviation and not only one standard deviation