Few teaching concepts have received as much attention in recent years as the Flipped Classroom (FC). This is clearly linked to media attention on the concept, which is currently being intensified by the Corona pandemic. In this research, the media rise of the concept is explained and the discrepancy between popularity and empirically validated research results is clarified. While the literature basis for the FC has grown enormously over the last decade, reviews and initial meta-analyses have shown, through their filter criteria, that not many of studies can meet scientific standards. The comparison of individual studies is particularly difficult, because there is no uniformly accepted framework and no uniform definition of the concept. For this reason, one of the goals of this research was to give an overview of the variety of FC definitions, discuss its most controversial characteristics, and to provide the key elements for a definition of the FC. A comparison of selected studies and reviews shows an assessment of the effectiveness of the teaching concept. The findings shed light on potential problems and challenges, and provide directions for future research.