No, I haven't gotten a question from a reader on this. But in my most recent post on Outside the Asylum, we have this explanation for non-Catholics who may read it:
The majority of the prayers offered during the Mass are fixed or with very limited options. The Ordinary of the Mass comprises these prayers and the order in which all the prayers and readings are said, complete with the congregation’s responses. There are, however, other prayers that vary with the seasons or with special dates in the Church’s life; together with the readings that are appropriate to the days, these all make up the Propers.
Since non-Catholics—at least those from a less liturgically-oriented communion—who come to a Mass often don't understand what's going on, it might help to go through each stage of the Mass.
This is a general overview of the Mass in the Ordinary Form, or Mass of Paul VI, which is a streamlined version of the Tridentine Mass. There are some differences if other Sacraments are to be performed, such as baptisms, weddings and ordinations, or if the celebrant is a bishop rather than a priest. There are also other licit forms besides the Tridentine that can be celebrated with the permission of the Ordinary, as well as those that are particular to religious orders.
There are two halves, if you will, to the Mass. The first half, called in the Tridentine form "the Mass of the Catechumens", consists of two parts: The Introductory Rites and the Liturgy of the Word.
In the Introductory Rite, we find a little bit of Christian archaeology: the Confiteor (L. "I confess"), a substituted litany that reminds us of when the earliest Christians confessed their sins in front of the whole Church (Didache 4; cf. Jas 5:16). We also find the only Greek prayer in the Latin rite, the Kyrie eleison ("Lord, have mercy"), for which non-Catholics with a background in classical choral music may know one or two settings. The whole effort is to prepare ourselves for the center of our worship; the penitential rite is our certification that we've prepared for the Mass beforehand by confessing our sins (a Catholic who is in a state of mortal sin isn't supposed to participate in Communion).
The Mass is not only for worship but also for instruction. In the Liturgy of the Word, we're given two readings from Scripture, one usually from the Old Testament and the other from Acts, the letters or Revelation (one reading on weekdays). Between the readings there's a responsorial psalm. Then we rise for the reading from one of the Gospels. All the readings are set according to a three-year cycle; if you were to attend Mass daily, you would hear almost all of the four Gospels, most of the rest of the New Testament and a good hunk of the Old Testament. After the homily, we then recite the Nicene Creed, then pray a litany called the Prayer of the Faithful, in which we as a community pray to God for certain intentions.
The second part of the Mass, called in the Latin Mass the Mass of the Faithful, starts with the collection and the offerings. In the days of the pre-Constantinian Roman Empire, those who hadn't been officially initiated into the Church were dismissed at this point; to this day, people undergoing the RCIA process of conversion are still dismissed, although we need no longer fear agents of the Emperor and non-Catholics not in the process still remain. (There's some kind of logic behind it, though I'm not yet privy to it.)
Speaking of which, there's also a certain logic to when we stand, sit and kneel; despite the jokes about "Catholic calisthenics". For most of our corporate prayers, we stand; we sit during the readings and during times of preparation.
During the Liturgy of the Eucharist, though, we spend much of our time kneeling in adoration and private prayer. Here is the center of our worship, during which the matter of the bread and wine become the true Body and Blood of Christ. For the non-Catholic, I have to stress this: The change is ontological, not merely symbolic. This belief is attested to by St. Paul (1 Cor 10:16, 11:23-29) as well as by the Church Fathers (e.g., St. Ignatius of Antioch, Letter to the Smyrnaeans 6:2, ca. 110 AD). Given our belief in the Real Presence of Christ in the Eucharist, kneeling in adoration makes sense ... there's simply not enough room for us all to prostrate ourselves.
(When does this change occur? The Latin Church holds that it occurs during the words of the Institution—"Take this, all of you and eat/drink from it"—while the Eastern Orthodox Churches believe that it begins with the beginning of the Eucharistic prayers and is consummated at the epiclesis, a prayer that specifically invokes the power of the Holy Spirit upon the gifts. Since the change isn't material, it can't be detected by scientific means right now; since the timing is speculative, there's room for accomodation in the name of reunion.)
Communion is the climactic moment of the Mass. "For as often as you eat this bread and drink the chalice, you proclaim the Lord's death until he comes" (1 Cor 11:26). So it's not surprising that, once Communion is concluded, not much happens: a couple of final prayers are offered, some brief announcements are made, then the celebrant blesses and dismisses the congregation. This is why the whole thing is called a "Mass": The last thing the celebrant or his deacon said in the old Latin form is Ite, missa est ("Go, it [the gospel message] is sent forth").
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Because the Mass is ordered around the celebration of the Eucharist, compared to some Evangelical or fundamentalist services little time is spent on reading or explaining Scripture. However, there's little in a properly celebrated Mass that doesn't refer back to Scripture or which doesn't instruct in the Faith. Once you understand the Eucharistic orientation, the rest of the Mass begins to make sense.
Unfortunately, though, the Eucharistic orientation doesn't explain why many priests' homilies are insipid, or why modern Catholic liturgical music blows, or why some celebrants and liturgical directors feel the need to stamp their own personalities on the rites through innovations such as liturgical dancing, puppets and (Deus nos adiuvat!) Clown Masses. Maybe Fr. Joseph O'Leary can explain how the Spirit of Vatican II led us to this point ... and why he's so concerned lest we roll back such progress.