Grace is the most distinctive concept in Christian theology, and the hardest to fully receive. It means unmerited favor — not just forgiveness for what you've done wrong, but acceptance that has nothing to do with what you've done right. That's a difficult truth for people who have been taught, explicitly or implicitly, that love must be earned.
Ephesians 2:8-9 is the clearest statement of grace in scripture: "For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast." The double negation — "not your own doing... not a result of works" — is emphatic. Salvation is entirely a gift. The reason given for this is striking: "so that no one may boast." Grace levels the ground.
2 Corinthians 12:9 is the most counterintuitive grace verse in this collection: "My grace is sufficient for you, for my power is made perfect in weakness." This is God's response to Paul's request for relief from suffering. The grace is not the removal of the difficulty — it's the sufficiency within it. That's a harder grace to receive than the grace that fixes things.
Romans 5:20-21 describes grace as something that "abounded all the more" where sin increased. That's not a license for sin — Paul addresses that directly in the next chapter — but it is a statement about the scale of grace. It is not a limited resource that runs out when you've used too much of it.
Hebrews 4:16 — "Let us then with confidence draw near to the throne of grace, that we may receive mercy and find grace to help in time of need" — is an invitation. The throne of grace is accessible. The posture is confidence, not groveling. That's what grace makes possible.