The answer
The catechumens are those who are being prepared to be baptized while the penitents are those who fell into certain sins and were asked — by their father of confession — to abstain from communion for a period of time. These two groups were designated an area in the church right by the main entrance in the very west of the church called, the narthex. There, the catechumens and the penitents would sit to participate in the Liturgy of the Catechumens or Liturgy of the Word.
Fr. Tadros Yacoub Malaty