The book contains an interpretative approach to forty-three psalms, most of which were presented in a series of lessons that looked at the declaration of terms of faith. For this purpose, the book of psalms was understood as if it were a book of the New Testament, i.e. written in the first way by the Church, a way of approach followed by almost all the Fathers who have given us interpretive notes on the psalms.
The main element of these lessons was to remind and clarify the terms of the faith. That is, in essence, to comment on and interpret the "what" of the Church - what the Church is. But also to describe the "how" of the Church - how the Church moves through History. They therefore have a catechism character, or, in simpler words, they are a catechism for adults.