loosely speaking the probability of an event is the number of positive outcomes divided by the number of all possible outcomes Throw a dice probability of getting a 3 is 1 6 But now consider something where you have an infinite number of possible outcomes pick a random number between 3 and 4 the probability of getting exactly pi is 1 infinity 0 However it is not impossible to get pi just very very unlikely Of course this is very much a theoretical concept since in pretty much all real world applications you have only a finite number of possible outcomes