The Mass of Pope Paul VI was introduced in 1969, after the Second Vatican Council. Commonly called the Novus Ordo, it is the Mass that most Catholics today are familiar with. Interest in the Traditional Latin Mass, celebrated in essentially the same form for the previous 1,400 years, has never been higher, largely because of Pope Benedict XVI's release of the motu proprio Summorum Pontificum on July 7, 2007, restoring the Traditional Latin Mass as one of two approved forms of the Mass.
There are many small differences between the two Masses, but what are the most obvious differences?
The Direction of Celebration
Traditionally, all Christian liturgies were celebrated ad orientem--that is, facing the East, from which direction Christ, Scripture tells us, will return. That meant that both the priest and the congregation faced in the same direction.
The Novus Ordo allowed, for pastoral reasons, the celebration of the Mass versus populum--that is, facing the people. While ad orientem is still normative (and is the only way that the Traditional Latin Mass is celebrated), versus populum has become the standard practice in the Novus Ordo.
The Position of the Altar
Since, in the Traditional Latin Mass, the congregation and the priest faced the same direction, the altar was traditionally attached to the east (back) wall of the church. Raised up three steps from the floor, it was called "the high altar."
For versus populum celebrations in the Novus Ordo, a second altar in the middle of the sanctuary was necessary. This low altar is often more horizontally oriented than the traditional high altar, which is usually not very deep but is often quite tall.
The Language of the Mass
The Novus Ordo is most commonly celebrated in the the vernacular--that is, the common language of the country where it is celebrated (or the common language of those who attend the particular Mass). The Traditional Latin Mass, as the name indicates, is celebrated in Latin.
What few people realize, however, is that the normative language of the Novus Ordo is Latin as well. While Pope Paul VI made provisions for the celebration of the Mass in the vernacular for pastoral reasons, his missal assumes that the Mass would continue to be celebrated in Latin, and Pope Benedict XVI has urged the reintroduction of Latin into the Novus Ordo.
The Role of the Laity
In the Traditional Latin Mass, the reading of Scripture and the distribution of Communion are reserved to the priest. The same rules are normative for the Novus Ordo, but again, exceptions that were made for pastoral reasons have now become the most common practice.
And so, in the celebration of the Novus Ordo, the laity have increasingly taken on a greater role, especially as lectors (readers) and extraordinary ministers of the Eucharist (distributors of Communion).
The Types of Altar Servers
Traditionally, only males were allowed to serve at the altar. (This is still the case in the Eastern Rites of the Church, both Catholic and Orthodox.) Service at the altar was tied to the idea of the priesthood, which, by its nature, is male. Each altar boy was considered a potential priest.
The Traditional Latin Mass maintains this understanding, but Pope John Paul II, for pastoral reasons, allowed the use of female altar servers at celebrations of Novus Ordo. The final decision, however, was left to the bishop, though most have chosen to allow altar girls.
The Nature of Active Participation
Both the Traditional Latin Mass and the Novus Ordo stress active participation, but in different ways. In the Novus Ordo, the emphasis falls on the congregation making the responses that were traditionally reserved to the deacon or altar server.
In the Traditional Latin Mass, the congregation is largely silent, with the exception of singing entrance and exit hymns (and sometime Communion hymns). Active participation takes the form of prayer and following along in very detailed missals, which contain the readings and prayers for each Mass.
The Use of Gregorian Chant
Many different musical styles have been integrated into the celebration of the Novus Ordo. Interestingly, as Pope Benedict has pointed out, the normative musical form for the Novus Ordo, as for the Traditional Latin Mass, remains Gregorian chant, though it is rarely used in the Novus Ordo today.
The Presence of the Altar Rail
The Traditional Latin Mass, like the liturgies of the Eastern Church, both Catholic and Orthodox, maintains a distinction between the sanctuary (where the altar is), which represents Heaven, and the rest of the church, which represents earth. Therefore, the altar rail, like the iconostasis (icon screen) in Eastern churches, is a necessary part of the celebration of the Traditional Latin Mass.
With the introduction of the Novus Ordo, many altar rails were removed from churches, and new churches were constructed without altar rails--facts that may limit the celebration of the Traditional Latin Mass.
The Reception of Communion
While there are a variety of approved forms for reception of Communion in the Novus Ordo (on the tongue, in the hand, the Host alone or under both species), Communion in the Traditional Latin Mass is the same always and everywhere. Communicants kneel at the altar rail (the gate to Heaven) and receive the Host on their tongues from the priest. They do not say, "Amen" after receiving Communion, as communicants do in the Novus Ordo.
The Reading of the Last Gospel
In the Novus Ordo, the Mass ends with a blessing and then the dismissal, when the priest says, "The Mass is ended; go in peace" and the people respond, "Thanks be to God." In the Traditional Latin Mass, the dismissal precedes the blessing, which is followed by the reading of the Last Gospel--the beginning of the Gospel according to Saint John (John 1:1-14).
The Last Gospel stresses the Incarnation of Christ, which is what we celebrate in both the Traditional Latin Mass and the Novus Ordo.