Tartarus is a place from ancient Greek mythology where bad people and monsters are punished for their bad behavior. It is like a really scary prison - kind of like when you have to sit in time-out, but for a really long time! It is said to be located deep below the ground, and it's said that no one can escape once they end up there. It's like a basement that nobody knows how to leave!
Those who did bad things and were very selfish or mean are sent to Tartarus as a punishment. They might be trapped there forever, or for a really long time, and they have to suffer for what they did. Tartarus is a very dark, cold, and eerie place. It's not a place you would ever want to visit, even in your dreams!
In Greek mythology, Tartarus was ruled by Hades, who was the god of the underworld. He was in charge of punishing the bad people and making sure they stayed in Tartarus. So if you were ever bad or mean to someone, remember that Tartarus might be waiting for you – so be kind and respectful to others!