Pow is the power function. Pow(x,n) means the variable x raised to the nth power. This is more commonly written as xn. As an example, pow(x,2) would be x-squared, or x2. Beginning in Grapher 13, when defining the fit equation, x^n can be used as an alternative to pow(x,n), but pow(x,n) is what is reported in the fit statistics.
Updated January 12, 2018