Here are some excerpts of the text from within the video:
“The art of the catacombs is very simple from the technical and formal point of view, but with very significant content. It shows how the first Christians represented the history of the Salvation with scenes from the Old and New Testaments, as well as other scenes and symbols that explain how to get to heaven.”
[...]
Throughout the catacombs are thousands of paintings with scenes from the Old and New Testaments.
The most repeated scene is that of Moses striking a rock with a stick, symbolizing faith in God. Which is followed by representations from the life of Jonah, meant to represent the Resurrection, and finally the miracle of the resurrection of Lazarus.
[...]
The archaeologist [Fabrizio] Bisconti has published the book “The paintings of the Roman catacombs,” where he ranks all of the underground paintings, and shows how the restoration work returns this art to its former glory. His book provides a detailed look into the life and death of early Christians.
