This document is an introduction to probability of compound events module. It begins with reviewing key concepts related to sets such as elements, cardinality, union, and intersection. These concepts are essential for understanding probability of compound events. The document then discusses probability as a measure of how likely an event is to occur. It defines probability of simple events as finding the probability of a single event and explains how to calculate it using ratios when outcomes are equally likely. An example problem demonstrates calculating probability. The introduction prepares the reader to learn about probability of compound events by refreshing important prior knowledge around sets and probability of simple events.