This book focuses on a central aspect of the subject-specific teaching competencies of educators: the ability to explain subject content ("explanatory ability"). The author specifically examines prospective teachers in the field of accounting (students of business education). To assess explanatory ability, domain-specific instruments are developed, utilizing a combination of quantitative and qualitative approaches. Initially, a paper-and-pencil test is used to capture the subject knowledge and subject-specific pedagogical knowledge of the teacher education students. Additionally, to achieve a practical assessment of explanatory ability, an interactive simulation (standardized explanation situation) is implemented. The work includes findings on the quality of explanations provided by prospective teachers as well as the influence of various learning opportunities.