Taken from No. 903, page 239; and No. 1348, page 340 of the Catechism of the Catholic Church, Libreria Editrice Vaticana: Urbi Et Orbi Communications:
[903]
Lay people who possess the required qualities can be admitted
permanently to the ministries of lector and acolyte (436) When the
necessity of the Church warrants it and when ministers are lacking,
laypersons, even if they are not lectors or acolytes, can also supply for
certain of their offices, namely, to exercise the ministry of the word, to
preside over liturgical prayers, to confer Baptism, and to distribute Holy
Communion in accord with the prescription of law." (437)
[1348]
All gather together. Christians come together in one place for the Eucharistic assembly. At its head is Christ Himself, the principal Agent of the Eucharist. He is high Priest of the New Covenant; it is He Himself Who presides invisibly over every Eucharistic celebration. It is in representing Him that the bishop or priest acting in the person of Christ the head (in persona Christi capitis) presides over the assembly, speaks after the readings, receives the offerings, and says the Eucharistic Prayer. All have their own active parts to play in the celebration, each in his own way: readers, those who bring up the offerings, those who give communion, and the whole people whose "Amen" manifests their participation.