What three traditional Catholic teachings were reaffirmed by the Church in the Council of Trent?

Catholic AnswerThere were many traditional teachings reaffirmed by the Council of Trent. That is just about all the Council of Trent did, of all the councils of the Church, it was far and away the most conservative breaking almost no new ground. Three traditional teachings included the Real Presence of Christ in the Eucharist, the necessity of the sacraments including confession and the priesthood, and the effectiveness of indulgences and praying for the dead - as noted in Scripture, the Second Book of Maccabees.

from A Catholic Dictionary, edited by Donald Attwater, Second edition, revised 1957

The Council of Trent

The 19th ecumenical council held at Trent in the Austrian Tyrol, 1545-63, summoned for the purpose of combating Protestantism and reforming the discipline of the Church; the longest and one of the most important of all general councils. It dealt in detail with the doctrinal innovations of the Reformers and with those gross abuses which gave them an opportunity to take root. It was one of the most important events of modern history and has had lasting effect. The principal dogmatic decisions were: the confirmation of the Nicene creed; the authenticity of the Latin Vulgate and the canonicity of all books contained therein and of them only; the definition of the doctrine of Original Sin; the precision of the doctrine of Justification, condemning justification by faith alone and imputation of grace; the condemnation of thirty errors about the sacraments; the definition of the Real Presence and of Transubstantiation as its mode: the precision of the doctrine of the sacraments of penance and Extreme Unction; the declaration that holy communion in both kinds was not necessary for lay-people and clerics not celebrating, Christ being received whole and entire under either species; the precision of doctrine concerning the sacrifice of the Mass and the sacraments of holy Orders and Matrimony; the affirmation of the doctrines of Purgatory, of the invocation of saints, and the veneration of them, their relics and images, and of Indulgences. Far-reaching decrees of reformation in discipline and morals were adopted involving many alterations in canon law, e.g. the decree Tametsi.