This introduction contains the current core knowledge of educational science regarding adult education in an understandable form. After explaining key terms such as adult education, further education, and lifelong learning, historical concepts of adult education are presented, along with a description of the essential theories and approaches relevant to the current discussion. This is followed by the key areas of action in adult education, which also represent the research fields of adult education science: target groups and participants, learning, knowledge and competencies of adults, institutions and learning locations, as well as professional practice in adult education. The volume concludes with a look at traditional paradoxes and current trends.