Salvator Mundi is a very fancy painting that some people believe was painted by a man named Leonardo da Vinci hundreds of years ago. The painting shows a man named Jesus wearing fancy clothes and holding a shiny crystal ball.
The reason why this painting is so special is because there aren't many paintings from Leonardo da Vinci that still exist today, and this one was lost for a long time until it was found again in 2005.
Since then, many people have tried to buy the painting for a lot of money, and it eventually sold for over $400 million in 2017. This makes it the most expensive painting ever sold!
Some people are still not sure if the painting is really by Leonardo da Vinci or if it's a fake, but either way, it's still a very famous and valuable piece of art that many people like to look at and talk about.