Imagine you have a bunch of toys, but you want to make sure that you play with all of them equally and treat them all fairly. That's kind of what the allgemeines gleichbehandlungsgesetz (AGG) is for people - it's a law that helps make sure that everyone is treated equally and fairly, no matter what.
So let's break it down a little further: The AGG is a law in Germany that says that nobody should be treated differently because of things like their skin color, their gender, their age, or their religion. That means that if you're a boy who wants to play with dolls, people shouldn't make fun of you or tell you that it's wrong, because the law says that you have the right to do what you want.
The AGG makes sure that everyone has the same opportunities to do things like get a job, go to school, or rent an apartment. That means that if you have a physical disability, for example, people can't say "No, you can't work here because you can't walk very well." They have to make sure that you have the same chance as anyone else to get the job, and that they treat you with respect and fairness.
In the same way, the AGG says that if someone does treat you unfairly, you have the right to do something about it. You can tell someone in charge, like a teacher or a boss, and they have to take your complaint seriously and do something about it.
So basically, the allgemeines gleichbehandlungsgesetz is a law that makes sure that everyone is treated the same way, no matter who they are. It's like a big rulebook for how to be fair and kind to everyone, and if anyone breaks those rules, there are things you can do to make sure it doesn't happen again.