In-group bias is when we like or favor people who are similar to us, like our family or friends. It's like having a special team of people on your team and you want to help them win.
It's like if you're part of a big family who loves sports, you are more likely to cheer for your family's sports team than if you're cheering for a team that you don't know anyone from.
When we're around people who are like us, it makes us feel good and safe. It's like having a big group of friends who like the same things you do. And because we feel good around them, we want to help them when they need us because that's what friends do.
But it's important to remember that just because someone is different from us, it doesn't mean they're bad or less important. We should always try to be kind and fair to everyone, even if they're not in our "team".