~from CNS (no attribution, just editorial board)!!
Here at a glance are the basic differences between the Tridentine Mass, promulgated in 1570, and the Roman Missal published in 1969 in response to the reforms called for by the Second Vatican Council:
-- While Latin is the original language of both liturgical texts, the new missal permits use of the vernacular language; because it called for full, active participation, the use of a local congregation's language became customary.
-- With the exception of readings for the feast days of individual saints, the Tridentine Mass has a one-year cycle of Scripture readings. The Vatican II liturgy has a three-year cycle for Sunday readings and a two-year cycle for weekday readings.
-- The old penitential "prayers at the foot of the altar," recited by priests and other ministers before Mass, were replaced by the penitential rite within the Mass, recited by the entire congregation.
-- In the Tridentine Mass, the first half of the liturgy was called the Mass of the Catechumens and almost always included a reading from one of the New Testament epistles and from one of the four Gospels. The new Liturgy of the Word, in accordance with ancient church tradition, almost always begins with a passage from the Old Testament.
-- The Liturgy of the Eucharist, formerly called the Mass of the Faithful, begins with the preparation of the gifts. The old offertory prayers were revised in the new liturgy to avoid what some people saw as a duplication of the eucharistic prayers.
-- Instead of one eucharistic prayer, there are now nine -- four for general Sunday and weekday use, two for Masses focusing on reconciliation and three for Masses for children.
-- In the new Mass, the Communion rite was simplified, allowing communicants to receive the Eucharist under the forms of both bread and wine.
-- The new Mass eliminated the recitation at the end of every Mass of what was known as the "last Gospel" -- the beginning of the Gospel of St. John.
-- A priest celebrated the Tridentine Mass facing east, which -- given the layout of most churches -- meant he celebrated with his back [gah!] to the congregation. Since the promulgation of the Roman Missal, the priest normally faces the congregation.