This textbook covers the most important concepts of elementary stochastic processes, and it becomes clear that they have a close relationship to real life. It is not a dry textbook; rather, it contains many supplementary remarks and illustrations alongside the teaching material. Some of the topics discussed can also be visualized through small computer programs available on the book's accompanying website. The book is well-suited for self-study as well. All new terms are thoroughly explained, and the proof structures are made as transparent as possible. A group of students has been intensively involved in the creation of the book. Content: How is randomness modeled? - Initial examples - Random variables - Conditional probabilities - The binomial distribution - The exponential distribution - Convergence of random variables.