This represents the conversion of Saul of Tarsus. He was a Roman, big on persecuting the Christians. In this painting he is temporarily blinded by the light of Christ and hearing Jesus words, which admonish him for his persecution. Saul became St Paul one of the early and most important apostles. His writings were the foundation for the New Testament.
Caravaggio was paid 300 scudi for this painting. Which was a pretty good chunk of change in its day. At the time a painters assistant might make about 30 scudi a year. The Scudo may have been worth about 75¢, but it converts to more than 20 times that in today’s currency. One hundred years before, Leonardo was paid about 100 scudi for a painting and Michelangelo was paid 200-450 per statue.
To see the original: https://bit.ly/2EqfuYX