This is a great question. If you did not know there is a huge debate between the ideas of a Counter Reformation and Catholic Reformation. The standard view for a long time was that the Catholic church sought a reformation in response to the Protestant Reformation. In light of this, many scholars called what the Catholics did at the Council of Trent a Counter-Reformation. The assumption behind this was that the Catholic church would have have not sought a reform apart from the works of the Protestants. A. G. Dickens is the scholar that pioneered this approach best.
Christopher Haigh, another scholar challenged this view by stating that the Catholic church sought reformation apart from the Protestants. Haigh states that there were many places that were completely untouched by the Protestant Reformation and that these groups were undergoing a reformation process themselves. In light of this, he, along with many revisionist scholars, call the council of Trent a step towards a Catholic Reformation.
The debate continues. The significance of what the Catholics did was to address some of the abuses of the church and made it more modern as it sought to address what the Protestants were saying and doing.