Grace is when God is not obliged to do something yet He does anyways. The best example of this is found in the sacrafice of Jesus Christ who deied for our sins so we might be restored to our relationship with the Heavenly Father. God sacraficed a part of Himself freely to accomplish this. He was not obligated to save us but did this because of His undying love for all of us. It is out of our power to save ourselves and we could never earn it so He has done it and made it free to whosoever believes.
Acts 15:11 No! We believe it is through the grace of our Lord Jesus that we are saved, just as they are.”
Galatians 3:18 For if the inheritance depends on the law, then it no longer depends on a promise; but God in his grace gave it to Abraham through a promise.