It is considered one of the most important councils in the history of the Roman Catholic Church, establishing church doctrine in response to the Reformation and condemning Protestantism. It clearly specified Catholic doctrines on salvation, the sacraments, the biblical canon, and standardized the Mass throughout the church, largely abolishing local variations. This became called the "Tridentine Mass", from the city's Latin name Tridentum.
Canon 1. "If any one saith, that man may be justified before God by his own works, whether done through the teaching of human nature, or that of the law, without the grace of God through Jesus Christ; let him be anathema."
Canon 4. "If any one saith, that man's free will moved and excited by God, by assenting to God exciting and calling, nowise co-operates towards disposing and preparing itself for obtaining the grace of Justification; that it cannot refuse its consent, if it would, but that, as something inanimate, it does nothing whatever and is merely passive; let him be anathema."
Canon 9. "If any one saith, that by faith alone the impious is justified; in such wise as to mean, that nothing else is required to co-operate in order to the obtaining the grace of Justification, and that it is not in any way necessary, that he be prepared and disposed by the movement of his own will; let him be anathema."
Canon 11. "If any one saith, that men are justified, either by the sole imputation of the justice of Christ, or by the sole remission of sins, to the exclusion of the grace and the charity which is poured forth in their hearts by the Holy Ghost, and is inherent in them; or even that the grace, whereby we are justified, is only the favour of God; let him be anathema."
Canon 12. "If any one saith, that justifying faith is nothing else but confidence in the divine mercy which remits sins for Christ's sake; or, that this confidence alone is that whereby we are justified; let him be anathema."
Canon 24. "If any one saith, that the justice received is not preserved and also increased before God through good works; but that the said works are merely the fruits and signs of Justification obtained, but not a cause of the increase thereof; let him be anathema."
Canon 30. "If any one saith, that, after the grace of Justification has been received, to every penitent sinner the guilt is remitted, and the debt of eternal punishment is blotted out in such wise, that there remains not any debt of temporal punishment to be discharged either in this world, or in the next in Purgatory, before the entrance to the kingdom of heaven can be opened (to him); let him be anathema."
Canon 32. "If any one saith, that the good works of one that is justified are in such manner the gifts of God, as that they are not also the good merits of him that is justified; or, that the said justified, by the good works which he performs through the grace of God and the merit of Jesus Christ, whose living member he is, does not truly merit increase of grace, eternal life, and the attainment of that eternal life, ...and also an increase of glory; let him be anathema."
- For additional detail see the Wikipedia article, Council of Trent.