Croatian nationalism means that people in Croatia believe that their country is very important and should be considered superior to other countries. It is like when you love something very much and think it's the best thing ever, like your favorite toy or your favorite food.
Some people in Croatia believe that their country should be independent and not have to listen to or follow the rules of other countries. They want to have control over their own government and their own laws.
However, not everyone in Croatia feels the same way. Some people believe that it is important to work with other countries and be part of a bigger group, like a family or a team, to help make things better for everyone.
It's important to remember that everyone is different, and it's okay to have different opinions and ideas. What matters most is that everyone respects each other and works together to create a better world for everyone.