Okay, kiddo. Do you know what a place is? Istria and Dalmatia are both places in Croatia, which is a country in Europe. A long time ago, there was a time when a lot of people had to leave those places all at once. This is called an "exodus."
The Istrian-Dalmatian exodus happened after World War II, which was a really big and scary war that lots of countries fought in. Istria and Dalmatia used to be part of Italy, but after the war, they became part of Yugoslavia, which was a different country.
Not everyone wanted to live in Yugoslavia, though. Some people who lived in Istria and Dalmatia were afraid of the new government there and wanted to leave. So lots of people left and went to other places, like Italy or South America.
It was a really sad time because families had to say goodbye and leave behind their homes and everything they knew. But, over time, many people who left were able to start new lives in other places and make new homes.