The aim of the essay is to communicate and make accessible to an audience of "non-experts" the essential meaning of theological discourse, of a discourse whose word and intelligence originate from the experience of God that becomes in following Jesus as a community of disciples. Hence the red thread that draws the path of these "lessons": God who says himself in Jesus Christ, thus saying himself and us in himself. Piero Coda explores some fundamental notions (which constitute the subject of the discipline that is usually called fundamental theology) regarding the knowledge of God - how can we know God? through which ways? -; to the revelation that he makes of himself fully and definitively in history in Jesus; to the Holy Spirit; to the Trinity and the history of its Christian experience and understanding from Saint Augustine to the present day. The discourse becomes more "current" in the last part in which the theological significance of the various religions in God's plan is outlined, and therefore in relation to Jesus and the Church, and the importance and method of dialogue between Church and religions.