The third edition of this textbook has been updated and expanded with several new chapters. It has consistently focused on an even stronger practical orientation. The chapters continue to follow the proven structure, providing an overview of the historical development of the topics from the beginnings of research to the current state of knowledge. The book is aimed at practitioners who, in their role as employees in the HR field, come into contact with the topics covered. Particularly in the areas of training, continuing education, and personnel development, the book can be very helpful. Another target audience is university and college students, for whom psychological knowledge can be of great importance for their future professional practice.