Okay kiddo, so you know how there are different types of churches, like Catholic, Baptist, and Methodist? Well, there are also some churches that believe something a little different about God.
You might have heard of the Trinity before - that's the idea that God is actually three "persons" in one: God the Father, Jesus the Son, and the Holy Spirit. But some churches don't believe in the Trinity. They think that God is just one person - kind of like how you're just one person.
These churches are called non-trinitarian, because they don't follow the Trinity idea. Some examples of non-trinitarian churches are Jehovah's Witnesses and Mormons.
Instead of believing in the Trinity, these churches might believe that Jesus was just a really important prophet, kind of like how some people think of Moses or Muhammad. They might also think that the Holy Spirit is more of a force or an energy, rather than a person.
It's not that non-trinitarian churches are necessarily better or worse than trinitarian churches - they just have a different way of understanding God. And that's okay! It's good that we can all have different beliefs and ideas, as long as we treat each other with kindness and respect.