Introduction: IT IS, unfortunately, a general observation that a large portion of today's Orthodox Christians are not sufficiently informed on matters of faith, worship, and life. They have only a little knowledge about these topics, sometimes incorrect, and even contrary to what the Church of Christ teaches, based on the Holy Scripture and its long Tradition. This observation is not ours. It is expressed or stated by official channels of their shepherds and ecclesiastical publications.

Bishops stated before the Hierarchical Synod: "Sermons are given, both verbally and in writing, but what is happening in the end, why does our people remain uncatechized? What is to blame?" (magazine "Church" 2010, p. 405). "Our people are uncatechized and let us wonder again whether this observation honors us, as well as who is responsible for the uncatechized state of our people" ("Church" 2013, p. 171).

Without intending to replace, even in the slightest, our ecclesiastical shepherds in their prophetic work, nor to ignore the existence of very important and extensive books by great authors who dealt with the relevant themes (which we recommend for study), in this current Series of brief volumes we offer to interested clergy – as an aid to their work – and lay readers, a concise "bouquet" of texts, which are easy to read, understandable, affordable (in a time of crisis), and aspire to provide the necessary knowledge to every Orthodox Christian.