Hey kiddo! Have you ever heard of the Delian League? No? Well, let me explain it to you!
So, back in ancient Greece, there were a bunch of city-states that were always competing with each other. One of these city-states was Athens. Athens was pretty powerful and had a lot of money, and they wanted to make sure they stayed that way.
So, Athens convinced a bunch of other city-states to join together in something called the Delian League. This was basically a club of city-states that agreed to work together and protect each other. They all gave money to Athens, who was in charge of the club, and Athens used that money to build a really strong navy.
The idea was that the navy would protect all the city-states in the Delian League from their enemies. But as time went on, Athens started using the money for its own purposes, like building cool stuff in their own city and paying for their own wars. The other city-states didn't like this very much, because they thought the money should be used for everyone's benefit, not just Athens'.
Eventually, some of the other city-states got mad and tried to leave the Delian League. But Athens wouldn't let them go, and even fought against some of them to keep them in. This made a lot of enemies for Athens, and eventually led to their downfall.
So, to sum it up, the Delian League was a club of city-states in ancient Greece that joined together to protect each other, but ended up being used by Athens for their own benefit, which caused a lot of problems.