Okay, so have you ever watched a sports game and cheered really loudly for your team? That's called being a fan and it's okay to support your team.
But sometimes, people take it too far and start hating other teams or countries just because they're not on your team. That's called jingoism.
It's like when a group of kids from one school doesn't like kids from another school just because they're from a different place. That's not fair or nice!
Jingoism is when people think their country is the best no matter what and they don't like other countries. We should respect other countries and their cultures, just like we want them to respect ours.
Remember, just like we have different favorite sports teams, there are lots of different countries in the world, and it's okay to like them all, not just one!