This lecture covers the fundamental concepts of random variables and their applications in information theory. It begins with an introduction to random variables, using examples such as snow conditions in Zermatt and Nendaz to illustrate the concept. The instructor explains the marginal distribution and how to calculate probabilities associated with random variables. The expected value of random variables is discussed, emphasizing its linearity and importance in modeling. The lecture also delves into the independence of random variables, providing definitions and examples to clarify the concept. The instructor introduces Shannon's entropy as a measure of uncertainty and information, contrasting it with Hartley's measure. Various examples, including weather forecasts and population statistics, are used to demonstrate how to calculate entropy and understand its implications. The lecture concludes with a discussion on the significance of entropy in computer science and its applications in data compression and information theory, setting the stage for further exploration in subsequent sessions.