In the previous section, we learned some basic probability rules, as well as some counting techniques that can be useful in determining the probability of an event using the classical approach. In this section, we'll explore discrete random variables and discrete probability distributions. The basic idea is that when certain conditions are met, we can derive formulas for calculating the probability of an event. Then, instead of returning to the basic probability rules we learned in the previous section to calculate the probability of an event, we can use the new formulas we derived, providing the certain conditions are met.