Usually refers to "z-standardization" which is shifting and rescaling data to assure they have zero mean and unit variance. Other "standardizations" are possible, too.

Specifically, when $(x_i), i=1, \ldots, n$ is a batch of data, its mean is $m=(\sum_i x_i)/n$ and its variance is $s^2 = v=(\sum_i(x_i-m)^2)/\nu$ where $\nu$ is either $n$ or $n-1$ (choices vary with application). Standardization replaces each $x_i$ with $z_i = (x_i-m)/s$.

Do not confuse standardization with or .