Grace is a theological concept, however, if you could see the grace that comes from God, I would picture it as the light rays in the picture above.
When I think of grace, I think of an endless supply of love that radiates down from heaven, so intense, however invisible, and that it covers the entire world. There is no escaping grace, unless you separate yourself from God, preventing his love (through your free will) from permeating you.
So what is Grace?
Grace is favor, the free and undeserved help that God gives us to respond to his call to become children of God, adoptive sons and daughters, partakers of the divine nature and of eternal life.
Grace is a participation in the life of God. It introduces us into the intimacy of Trinitarian life: by Baptism a Christian participates in the grace of Christ, the head of his Body. As an "adopted son" we can henceforth call God "Father," in union with the only Son. We receive the life of the Spirit who breathes charity into us and allows us to form the Church.
This vocation to eternal life is supernatural. It depends entirely on God's gratuitous initiative, for He alone can reveal and give himself. It surpasses the power of human intellect and will, as that of every other creature.
The grace of Christ is the gratuitous gift that God makes to us of his own life, infused by the Holy Spirit into our soul to heal it of sin and to sanctify it. It is the sanctifying or deifying grace received in Baptism. It is in us the source of the work of sanctification:
Therefore if any one is in Christ, he is a new creation; the old has passed away, behold, the new has come. All this from god, who through Christ reconciled us to himself.