With the rapid developments in hardware technologies, distributed computing and the interconnected world became realities, and the term "communication" became central in computer science. Solving communication tasks under different circumstances is the topic of this textbook. It provides an introduction to the theory of design and the analysis of algorithms for the dissemination of information in interconnection networks, with a special emphasis on broadcast and gossip. The book starts with the classic telegraph and telephone communication modes and follows the technology up to optical switches. Despite the rigorous presentation, simplicity and transparency are the main learning features of this book. All ideas, concepts, algorithms, analyses and arguments are first explained in an informal way in order to develop the right intuition, and then they are carefully specified in detail. This makes the content accessible for beginners as well as specialists.