When we talk to people, we use words like "he" or "she" to describe them. But sometimes, a person might not feel like those words fit them very well. Maybe they feel more like a boy sometimes, and more like a girl other times. Or maybe they don't feel like a boy or a girl at all! That's okay, because people can be different in lots of ways.
To help make everyone feel comfortable and respected, we can ask people what their "preferred gender pronoun" is. A "pronoun" is just a word we use instead of someone's name or "he" or "she". So, if someone told you that their preferred gender pronoun was "they", that means you would use the word "they" instead of "he" or "she" when you talk about them.
It's important to use someone's preferred gender pronoun because it shows that we respect them and want to make them feel comfortable. And if we accidentally use the wrong pronoun, we can always say sorry and try to do better next time!