Being fueled by continual development of permanent-magnet (PM) materials and machine structures, PM machines are becoming attractive for a wide range of applications. In this article, the magnet-materials that have been used for PM machines are first introduced. Then, the classification of various PM machines is discussed. Consequently, major PM machines are described, with emphasis on their machine structures and operating principles. Also, the corresponding variants due to morphological changes are discussed. Finally, a quantitative evaluation of those viable PM machines is given to identify their prospects and potential applications.