What is "mass of the catechumens"

The Mass (or Liturgy) of the Catechumens is an ancient title for the first half of the Roman Catholic or Eastern Orthodox worship service known as the Mass or Divine Liturgy. This part of the Mass is now referred to by the Catholic Church as the Liturgy of the Word. It was originally called the Mass of the Catechumens, because the Catechumens, or candidates for Baptism, were required to leave the ceremony before the beginning of the Liturgy of the Eucharist, or Mass, proper.

This exclusion was enforced on the grounds that until Baptism, persons were not fully members of the Church and should not participate in the communal sacrifice that symbolizes and embodies the spiritual union of the Faithful, according to Catholic belief.

In the earliest liturgy there was a service consisting of readings, a homily (explanation of the readings and how to apply them to one's life) and petitionary prayers based on the readings and homily (bidding prayers or prayers of the faithful).