We look at the Protestant Reformation and what brought it about. We theologically deal with Justification by faith and how this has been misunderstood in both Protestant and Catholic Christianity. We also look to the question what have we gained and what have we lost since 1517 and is there any reconciliation.
For more on this topic here are some great sources:
http://www.thecounciloftrent.com/ch6.htm
https://reformationbiblecollege.org/blog/the-five-solas
https://www.catholic.com/tract/myths-about-indulgences
https://www.ligonier.org/blog/reformation-and-men-behind-it/