This book is meant to be an instrument at the service of catechesis, both for those who give catechism classes and for those who wish to know more about the basic theological notions of the Christian faith. Instead of following the traditional way of explaining the Creed, which means starting from the top, the mystery of the Trinity, it goes through the simpler path of what was humanly seen, that is Jesus, his teaching, death, and resurrection, to come to talk about the divine realities that one cannot see. Although it deals with some difficult theological issues, overall it uses a simple language, comprehensible by non-specialized people. The long pastoral experience of the author provided the necessary understanding to put theological knowledge at the service of pastoral concrete needs.