Okay kiddo, do you know what gender is? It means whether you are a boy or a girl. Sometimes people feel like they aren't just a boy or a girl, they might feel like they are both or neither. That's called being non-binary.
Now, people use symbols to represent these different genders. The boy symbol usually looks like a circle with a line sticking out on the side, kind of like a stick figure with arms. The girl symbol looks like a circle with a cross underneath it, like a plus sign.
But sometimes people want to use different symbols to represent themselves. There are symbols for non-binary people too, like a combination of the boy and girl symbols or a circle with an X in it.
These symbols help people show who they are without having to say it out loud every time. It's like using a secret code so other people who understand it can identify with you.