International audienceThe attempt of this lecture is to give a theoretical framework for the teacher's activity. We will consider several levels for this activity, and the interactions between these levels. The nature of these interactions will require the consideration of the situation of the teacher, and the characterization of different ‘milieu'. We will therefore consider our model of the teacher's activity as a theoretical and as well a technological model, and we will show a partial application.L'ambition de ce texte est de donner un modèle théorique pour l'activité du professeur. Nous considérons plusieurs niveaux de cette activité ainsi que les interactions entre ces niveaux. La nature de ces interactions demande de considérer la si...