BlueCalculus, the binomial distribution has three parameters n, x, and p. The parameter n represents the number of trials performed which are each assumed to be independent bernoulli trials, x represents the value we want to find the probability of for example x takes on only discrete values of 0,1,2,3,...... and p represents the probability of success and its complement q = 1-p represents the probability of "failure" or in other words the probability that the event does not happen. The Actex manual again has some really good examples using this distribution.