The Bosnian War happened a long time ago, when many people in a place called Bosnia didn't get along with each other. There were three main groups of people: the Bosniaks (who are mostly Muslim), the Croats (who are mostly Catholic), and the Serbs (who are mostly Orthodox Christian).
Some people thought that only people who were like them should live in Bosnia, so they started fighting. The war went on for a really long time, from 1992 to 1995, and lots of people got hurt or killed. Many people had to leave their homes and go to other countries because it wasn't safe to stay in Bosnia.
Other countries, like the United States and some in Europe, tried to help stop the fighting and bring peace to Bosnia. Eventually, after lots of talks and negotiations, the war ended and a peace agreement was signed in 1995.
Now, people in Bosnia are trying to live together peacefully and rebuild their country. It's been a long and difficult process, but they're making progress.