In Orthodoxy, a catechumen is someone who has formally entered the process of being instructed in the Christian faith in preparation for baptism and entrance into the Holy Church. This is not a casual inquirer, but one who has undergone the service of the making of a catechumen, where exorcisms are read, the Creed is proclaimed, and the individual is received under the spiritual care of the Church. Catechumens are not yet baptised, chrismated, or permitted to receive the Holy Mysteries.
The Orthodox Church distinguishes between the faithful and the catechumens liturgically and spiritually. During the Divine Liturgy, catechumens are present during the first part, the Liturgy of the Word, and are then dismissed before the Liturgy of the Faithful. This practice preserves the understanding that the Mysteries of the Church are reserved for the baptised faithful.
Regarding prayer with catechumens, we may and do pray for them. In the Divine Liturgy, the deacon or priest says, “Let us pray to the Lord for the catechumens,” followed by petitions for their enlightenment, instruction, and eventual baptism. However, praying with catechumens, especially in an interconfessional or pan-religious setting, is not permitted. Prayer is an expression of shared faith. Since catechumens have not yet been fully joined to the Church, joint prayer in the full ecclesial sense is reserved until after their baptism.
St. Cyril of Jerusalem, in his Catechetical Lectures, instructed the catechumens but was firm that the full mystery of the faith, particularly the Eucharist, would only be explained after baptism. This is a principle the Church has held from the earliest centuries.
We pray for catechumens, but we do not engage in full liturgical or spiritual prayer with them as with the baptised faithful, until they are united to the Church through the Mysteries.
— Br. Jon.