This book portrays the distributions that are fundamental for enterprise risk management and shows when and how they are used. These include the Bernoulli distribution, the binomial distribution, the Poisson distribution, the uniform distribution, the triangular distribution, the PERT distribution, the modified PERT distribution, the trapezoidal distribution, the custom distribution, the normal distribution, the lognormal distribution, the Weibull distribution, the expert distribution, the poly distribution and the compound distribution. Furthermore, the book explains how the parameterisation of the distributions can be done via expert estimates or algorithmic calibration.