Computation
When order is not important.
Permutation
Number of arrangements of n objects can have when r of them are used.
When order is important.
Binomial Distribution
Categorizes results of a number of repeated Bernoulli trials and the outcomes of those trials.
Binomial Distribution can be used if:
There is a nearly infinite number of items or a steady stream of items being produced.
The outcome is Bernoulli, that is, it can be classified as either a success or a failure.
Poisson Probability Distribution
Quantifies the count of discrete events.