Programme for International Students Assessment (PISA) originated in the end of the 1980s, when there was an intense debate in this organization on how to influence the course of the education policies of member states. This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book highlights how PISA has given rise to an international space of circulation between science, expertise and policy despite increasing criticism. It describes a study about how students from different age groups, education levels and courses answer PISA items and how they evaluate different aspects of these items. The book underlines that the international large-scale assessment studies have acquired great importance in recent decades.