"Rather like a comic book without words, Giotto tells the story of Christ and his parents through pictures. Most of the population of Europe was illiterate at this time and so couldn't read the Bible for themselves (Bibles were rare and expensive in any case—there was no printing press and so each was copied by hand). People learned the stories of the Bible—stories that would help them get to heaven—by hearing the words of the priest in the church, and by looking at paintings and sculptures."
Dr. Zucker, Steven , and Beth Dr. Harris. "Giotto, Arena (Scrovegni) Chapel." Khan Academy. October 3, 2021.