Gamma Command

Gamma( <Number α>, <Number β>, x ): Creates the cumulative distribution function (cdf) of a Gamma distribution with parameters α, β at v, that is the probability P(X≤v) where X is a random variable with a Gamma distribution with parameters α and β.
Gamma( <Number α>, <Number β>, x, <Boolean Cumulative> ): If Cumulative is true, creates the cumulative distribution function of a Gamma distribution with parameters α and β at the variable value v. If Cumulative is false, it creates the probability density function (pdf) of the corresponding Gamma distribution at v.
Gamma( <Number α>, <Number β>, <Variable Value v> ): Calculates the value of cumulative distribution function of gamma distribution at v, i.e. the probability P(X≤v) where X is a random variable with gamma distribution given by parameters α, β.

Returns the probability for a given x-coordinate’s value (or area under the gamma distribution curve to the left of the given x-coordinate).