I present some key ideas and examples of (mainly French) work in the didactics of mathematics with the aim of identifying the didactics approach to education in relation to more general approaches. In particular I discuss three crucial features of didactics: (1) its epistemological character, i.e. the central focus on specific knowledge in different forms, and the conditions for enabling pupils to acquire it; (2) its relations to the background science (in casu, mathematics as a science); and (3) its actual and potential roles in relation to teaching and teachers (in particular, didactics as a design science and as a part of teachers' education and professional knowledge base). (Contains 3 figures and 12 notes. More about the puzzle situation (see Figure 1) is appended.)