Original: The Tridentine Mass is the form of the Roman Rite Mass contained in the typical editions of the Roman Missal that were published from 1570 to 1962. It was the most widely celebrated Mass liturgy in the world until the introduction of the Mass of Paul VI in December 1969.
Simplified: Tridentine Mass is the name given to a Roman-rite catholic mass, as it was common before 1969.