Probability brings together the mathematical rules that enable us to calculate the chances that an event will occur.

Its origin lies in the resolution of problems presented by games of chance. Thus, the probability of obtaining a 6 on rolling one sole die is 1/6. But the frequency observed for this event can differ from this theoretical value. The frequency approaches the probability when there are a a great number of rolls. When the law of probability follows a constant law, we say that all events are equiprobable. The probability of an event is always less than or equal to 1. The sum of the probabilities of all possible events is 1.