Gender neutrality is when we don't assume someone's gender. It means we don't use words that tell the listener whether they are a boy or a girl. In some languages, like English, we don't have gendered pronouns for everyone, like "they" can refer to anyone. But in other languages, like Spanish or French, the pronouns are gendered.
Let's take an example in Spanish. If you are talking about a person and you don't know their gender, you can't use "he" or "she". Instead, you would use "el" if you are guessing it is a man, or "ella" if you are guessing it is a woman. But this assumes you know what gender the person is, which we don't always know. So, to be more inclusive, some people propose using a different word that doesn't indicate gender. For example, instead of saying "el" or "ella", we could say "elle" (invented for this purpose) or use "they" (even though it is traditionally used for plural, it can now also indicate a singular person with an unspecified gender).
The debate around this is not only about language but also reflects the idea that we should treat everyone equally regardless of their gender. By using gender-neutral language, we create a more inclusive society where people feel respected and recognized, no matter what their gender.