Okay, so let's pretend that we are a bunch of kids playing in a playground. Now, imagine that some kids in the playground decide that they want to be in charge of everything that happens. They may say something like, "We are the boss and you have to do what we say."
But imagine that they don't just stop there. They may also start treating some other kids differently based on certain things they cannot change, like the color of their skin or where their family comes from. They may not let these kids play certain games, use certain playground equipment, or even let them share snacks with others.
Now, this would be really unfair, right? It would make the kids who are being treated differently feel really sad and left out. This kind of unfair treatment is called apartheid.
In the real world, some countries have done this same kind of thing, but with grown-up problems instead of playground games. They may make rules that only certain people can vote or go to school, or they may not let some people work certain jobs or live in certain areas based on things like their race.
This is very wrong and can cause a lot of harm to the people who are being treated unfairly. That's why it's important to speak up and make sure everyone is treated the same, no matter who they are or where they come from.