In this paper, I present and discuss some important concepts from Michel Foucault's theory of discourse, specially the concepts of statement, discoursive practice, subject and discoursive heterogeneity. From this theoretical reference, I explain the intimate relation between discourse and power, as well as several and complex forms to investigate "expressed things". The aim is to indicate productive contribution of this theoretical and methodological reference to educacional researches which intend to "analyze discourses".