This introduction presents an overview of key concepts discussed in subsequent chapters of this book. The book introduces basic terms and laws concerning energy conversion from one form into another, yet from an engineering point of view and with a particular focus on transport and industrial applications. It addresses curious readers of engineering-technical literature, persons who are directly involved in investments in new energy-related technologies such as contractors, civil servants, bank project supervisors, or simply people who see the topic of energy as an intellectual challenge. The book discusses some basic types of energy conversion referred to as thermal-energy technologies, such as heat-mechanical energy conversion, heat-electric energy conversion and regeneration and recuperation of thermal energy. It also discusses available energy resources and energy strategies employed to decrease the import of energy sources by increasing the efficiency of energy generation and reducing losses via energy saving in basic economy trends transport, industry, and households.