Short answers, pulled from the story.
The Greek word charis translates to that which brings delight, joy, happiness, or good fortune. This term appears in the Septuagint translation of Genesis 6:8 to describe why God saved Noah from the flood.
In the Eastern Orthodox Church, grace is identified with the uncreated Energies of God and is considered partaking of the Divine Nature described in 2 Peter 1:4. Grace is the working of God himself rather than a created substance, and it cannot be treated like a commodity.
The Council of Trent met in 1547 to address Protestant objections regarding grace and justification. It aimed to purge the Roman Catholic Church of controversial movements and declared justification and sanctification are elements of the same process.
Martin Luther posted ninety-five theses to church door in Wittenberg in 1517 because this act was precipitated by arrival of Johann Tetzel authorized to sell indulgences. Indulgences were predicated on doctrine of treasury of grace proclaimed by Pope Clement VI.
Calvinist theology defines salvation as process where God alone is author and works entirely through grace without human participation. Dutch theologian Jacobus Arminius formulated Arminianism beginning 17th century which affirms compatibility between free will and divine foreknowledge.