Novus Ordo Mass
The Novus Ordo Missae (New Order Mass), that was changed in The Church during Vatican II, has altered the way that Jesus intended the mass to be held throughout His church.
The difference between the 2 masses is simply described in this manner, according to Real Catholicism, 6/7 Volume I (found on this website):
Traditional Latin Mass (Council of Trent) The Mass is the true and special sacrifice of the New Law. In it Jesus Christ, by the ministry of the Priest offers His Body and Blood to God the Father under the appearances of bread and wine by a mystical immolation in an unbloody manner for a renewal and memorial of the Sacrifice of the Cross.
Novus Ordo Missae (Pope Paul VI) The Lord’s supper, or Mass, is the assembly, or gathering together, of the people of God with the priest presiding to celebrate the memorial of the Lord. For this reason the promise of Christ is particularly true of the local congregation of the Church: “Where two are three are gathered in My Name, there I am in the midst of them.”
Watch these short videos to learn the differences:
“To tell the truth, it is a different liturgy of the Mass. This needs to be said without ambiguity: the Roman Rite as we knew it no longer exists. It has been destroyed.” – Joseph Gelineau, SJ, one of the experts involved in its formulation (The Tridentine Mass, p. 39)
According to Cardinals Ottaviani and Bacci, in their study and letter to the Pope, the New Mass “teems with insinuations or manifest errors against the integrity of the Catholic Faith.”
“Here the [Protestant] Lord’s Supper and the [Catholic] Mass are merged into one … In the present ecumenical context, it is as if neither Luther nor the Council of Trent ever happened.” (Who Shall Ascend, p. 534)
Here is a side-by-side comparison of the two masses: