This book has been prepared on the basis of church doctrinal literature and the most famous works of Orthodox spiritual authors. The most important and most useful information about the foundations of the Orthodox faith and practical recommendations for believers are collected and thematically distributed into sections: the Sacraments of the Church, worship, the laws of spiritual life, prayers, fasting and holidays with useful instructions from St. John Chrysostom, St. Ignatius Brianchaninov, Archbishop Averky ( Taushev), Bishop Theophan the Recluse, Archpriest Seraphim Slobodsky, Archbishop John (Shakhovsky) and many others. The book is recommended for distribution by the Publishing Council of the Russian Orthodox Church.