God’s “Grace” is something – it is not just a word.
It is God’s favor (an act of kindness beyond what is due or usual).
Grace is defined in the Catechism of the Catholic Church as: "grace is favor, the free and undeserved help that God gives us to respond to his call to become children of God, partakers of the divine nature and of eternal life".
Grace is a participation in the life of God, which is poured unearned into human beings, whom it heals of sin and sanctifies. The human will can resist grace if it chooses. It is not like a lifeless thing, which remains purely passive.
There are TWO forms of God’s grace.
Sanctifying/Habitual Grace and Actual Graces
According to the Catechism of the Catholic Church, sanctifying grace is a habitual gift, a stable and supernatural disposition that perfects the soul itself to enable it to live with God, to act by his love. (1) Habitual grace, the permanent disposition to live and act in keeping with God's call, is (2) distinguished from actual graces which refer to God's interventions – God taking action to bestow His grace (favor) on a person for a particular reason or reasons.
The infusion of sanctifying grace, says the Church, transforms a sinner into a holy child of God, and in this way a person participates in the Divine Sonship of Jesus Christ and receives the indwelling of the Holy Spirit. Sanctifying grace remains permanently in the soul as long as one does not reject one's adopted sonship.
St. Thomas Aquinas
According to a commonly accepted categorization, made by St. Thomas Aquinas in his Summa Theologiae, grace can be given either (1) to make the person receiving it pleasing to God so that the person is sanctified and justified - (2) or else to help the receiver lead someone else to God.
Examples: (1) Sanctifying/Habitual Grace
John 1: 14 The Word became flesh, he lived among us, and we saw his glory, the glory that he has from the Father as only Son of the Father, full of grace and truth. 15 John witnesses to him. He proclaims: ‘This is the one of whom I said: He who comes after me has passed ahead of me because he existed before me.’ 16 Indeed, from his fullness we have, all of us, received—one gift replacing another, 17 for the Law was given through Moses, grace and truth have come through Jesus Christ.
Act 15: 11 But we believe that we are saved in the same way as they are: through the grace of the Lord Jesus.’ 12 The entire assembly fell silent, and they listened to Barnabas and Paul describing all the signs and wonders God had worked through them among the gentiles.
Paul’s letter to the Romans: Romans 3: 22 God’s saving justice given through faith in Jesus Christ to all who believe. 23 No distinction is made: all have sinned and lack God’s glory, 24 and all are justified by the free gift of his grace through being set free in Christ Jesus. 25 God appointed him as a sacrifice for reconciliation, through faith, by the shedding of his blood, and so showed his justness; first for the past, when sins went unpunished because he held his hand; 26 and now again for the present age, to show how he is just and justifies everyone who has faith in Jesus.
Romans 5: 17 It was by one man’s offence that death came to reign over all, but how much greater the reign in life of those who receive the fullness of grace and the gift of saving justice, through the one man, Jesus Christ.
Romans 5: 20 When law came on the scene, it was to multiply the offences. But however much sin increased, grace was always greater; 21 so that as sin’s reign brought death, so grace was to rule through saving justice that leads to eternal life through Jesus Christ our Lord.
Romans 11: 5 In the same way, then, in our own time, there is a remnant, set aside by grace. 6 And since it is by grace, it cannot now be by good actions, or grace would not be grace at all!
Examples: (2) Actual graces which refer to God's interventions
Acts 6: 8 Stephen was filled with grace and power and began to work miracles and great signs among the people.
Romans 15: 16 But I have special confidence in writing on some points to you, to refresh your memories, because of the grace that was given to me by God. 16 I was given grace to be a minister of Christ Jesus to the gentiles, dedicated to offer them the gospel of God, so that gentiles might become an acceptable offering, sanctified by the Holy Spirit.
Paul’s letter to the Corinthians: 1st Corinthians 3: 10 By the grace of God which was given to me, I laid the foundations like a trained master-builder, and someone else is building on them.
1st Corinthians 15: 9 For I am the least of the apostles and am not really fit to be called an apostle, because I had been persecuting the Church of God; 10 but what I am now, I am through the grace of God, and the grace which was given to me has not been wasted. Indeed, I have worked harder than all the others—not I, but the grace of God which is with me.
2nd Corinthians 9: 8 God is perfectly able to enrich you with every grace, so that you always have enough for every conceivable need, and your resources overflow in all kinds of good work.
Paul’s letter to the Hebrews: 4: 16 Let us, then, have no fear in approaching the throne of grace to receive mercy and to find grace when we are in need of help.
Hebrews 13: 8 Jesus Christ is the same today as he was yesterday and as he will be forever. 9 Do not be led astray by all sorts of strange doctrines: it is better to rely on grace for inner strength than on food, which has done no good to those who concentrate on it.
Paul’s letter to James: James 4: 6 But he has given us an even greater grace, as scripture says: God opposes the proud, but he accords his favor to the humble. 7 Give in to God, then; resist the devil, and he will run away from you. 8 The nearer you go to God, the nearer God will come to you.
Paul’s letter to Peter: 1st Peter: 10 Each one of you has received a special grace, so, like good stewards responsible for all these varied graces of God, put it at the service of others. 11 If anyone is a speaker, let it be as the words of God, if anyone serves, let it be as in strength granted by God; so that in everything God may receive the glory, through Jesus Christ, since to him alone belong all glory and power for ever and ever. Amen.