I love this story. It's about food. You really don't need much background to enjoy it and to understand its point.
The idea of feeding the gods is pretty common in antiquity. That's what sacrifices are for. In most cases the priests eat the food. In other cases, animals come to consume it. There's a temple to Ganesh in India where rats eat the sacrifices! In ancient Babylon the feast for Marduk (here called Bel) was taken to the king. In this story, though, the king doesn't get the food. He believes Bel eats it. Daniel — clever as he was in Susanna — devises a trick to get the priests to reveal that they are really the ones eating the sacrifice.
Before you ask: we have no idea what the dragon might have been. Maybe it was a really big snake. Who knows? The point is that, unlike the idol of Bel, the dragon is really living. It can eat. Whereas before Daniel's actions concerned a god who couldn't eat and resulted in the death of priests, now his actions concern an animal who can eat and result in its own death. In both cases the God of the Jews is affirmed as a living God.
Finally, the religiously serious of Babylon have had enough of this Jewish interloper interfering with their gods. They have him thrown the lions. This time Daniel gets to eat and so do the lions. The persecutors became an unexpected meal themselves.
Great story, no? Hmm…let's go see what's in the fridge.