All types of piston machines, especially internal combustion engines as well as piston pumps and compressors, but also machines with rotating displacement such as the Wankel engine and rotary compressors, can be found today in vehicles as well as in small and large stationary or mobile plants and units. Despite the diverse functions of piston machines, they share many similarities in terms of structure and operation, such as periodic operation, charge exchange, and the compression and expansion processes. In this context, pumps can be considered as a special case. The aim of this textbook is to highlight these commonalities inherent to all machines and to relate the apparent diversity to the universal principles that apply to all machines. The book is intended to serve as a concise guide for students and also for engineers in practice.