Perhaps it would be wise to state more specifically what is meant by "grace". Rather than trying to come up with a single definitive answer, I've asked a distinguished panel of experts (i. e., my friends).
Grace is available to everyone, just for the asking. (Given - Reaching to All - Christ's Everlasting (love)) Grace is the foundation of God's love, the complete sufficiency of the Lord's presence expressed in our own lives. Grace...yes, some things are for free. Grace, our gift from Him. Grace, our goal to give others.
The simple answer is that grace is Gods unmeritted favor given to the undeserving sinner. But it is so much more than that. So much more as to put us in awe of the mercy of God. When we sin against someone, and repent of the wrong we have done, and are pardoned for our action, that is forgiveness. When we forgive someone who has repented 77 times 7 times a day, we are following Christ's admonition and have gone beyond forgiveness into forbearance and patience. But God goes even further, way beyond the "extra mile". When we are forgiven even for the things that we are not able, and perhapps even unwilling to repent of, just for our decision to trust in God, that is grace.
When our Lord was beaten, abused, and nailed to a cross, and the crowds stood jeering at him, and he said "Father forgive them, they don't know what they are doing!"... That is grace. When the Lord promissed in prophesy to write his laws in the hearts of un repentant Israel, and MAKE them his children, and He their God, and "remember their sins no more", that is grace. When he has shown us the wisdom of all His laws, and we come in all honesty and humility and say "God, I just can't do all this", and he offers to GRANT us HIS righteousness in exchange for ours, and an unconditional pardon for the "wages" of all our wrongdoing, past, present, and future, as a free gift, if only we are willing to believe and receive... THAT is grace. "My Grace is sufficient for you" He decleares in the book of Romans. And we are without excuse if we don't receive it, for the gift truly is free.
I like waht Randy wrote and would suggest that the idea that "our salvation is by grace and grace alone" that good works is not necessary, but asking for Jesus to be our Lord and Savior and repenting of our sins prvides us with this Grace that we all are so unworthy of save the atonement of our sins by Jesus.
The question of grace initially seemed perplexing. At first, then the answer seemed clear. Then it got fuzzy as I tested the answer. Then I applied Occams razor-Keep Iit Simple So anyone can understand.
What is Grace?
An undeserved reward. There is a "grace period" on bills. We use the term "grace" when blessing meals. However, the most important Grace is the Salvation The Creator God has provided for His creation's Redemption. Grace, like any gift must be received. We all must choose to receive any gift upon offering. Those who chose not to accept the gift (or those who have not chosen to accept the gift) do not have the gift.
To some my whittling with Occams razor may seem sharp or cruel: Nothing like an eternity away from love (which is the alternative).