Faith is the theological virtue by which we believe in God, all that He has said and revealed to us and the Holy Church proposes to us, while Understanding is a gift of the Holy Spirit that allows us to penetrate the truths of the Faith and ensure our beliefs, in a certain and limited way.
Wisdom makes the soul responsive to the Counselor in the contemplation of God to use of God’s ideas to judge His creation. Wisdom is the desire to contemplate God’s ideas, whereas Understanding allows us to penetrate such ideas to become convinced of the truths of the Faith.
We can also infer conclusions from the Faith to derive a deeper meaning of man’s role in the world and his relation to God. Natural reason is just concerned with the material world, while Understanding helps us to orient our actions toward God and place our lives in the context of eternal law and our souls in the relation to God.
Jesus explained the Scripture concerning Him to two disciples on the road to Emmaus … Then their eyes were opened and they recognized Him … (Luke 24:13-35) This is an example of Understanding the Comforter grants us, as He wills.