From YOUCAT, page 307:
307: What is faith?
Faith is the power by which we assent to God, acknowledge his truth, and commit ourselves personally to him. [1814–1816, 1842].
Faith is the path created by God leading to the truth that is God himself. Because Jesus is “the way, and the truth, and the life” (Jn 14:6), this faith cannot be merely an attitude or “confidence” about something or other. On the one hand, the faith has definite contents, which the Church professes in the Creed (= profession of faith), and it is her duty to safeguard them. Anyone who wants to accept the gift of faith, in other words, anyone who wants to believe, acknowledges this faith, which has been preserved constantly through the ages and in many different cultures.
On the other hand, part of faith is a trusting relationship to God with heart and mind, with all one’s emotional strength. For faith becomes effective only through charity, practical love (see Gal 5:6). Whether someone really believes in the God of love is shown, not in his solemn affirmations, but rather in charitable deeds.