Okay, so I'm going to explain ius gentium to you like you're 5 years old.
Ius gentium is a Latin word that means "law of nations." It's a special kind of law that was used a long, long time ago by the Romans.
You see, back then, different countries and cultures had their own laws and customs. But sometimes, when people from different places came together, they needed a set of rules that everyone could agree on. And that's where ius gentium came in.
It was like a big book of rules that everyone could use when they were in a different country or culture. It covered things like trade, marriage, and war - all the important stuff that people needed to know about.
So basically, ius gentium was a way for everyone to get along and understand each other, even if they came from different places with different laws. Pretty neat, huh?