Okay kiddo, so when people talk about a "canon" they're usually talking about a bunch of stories or information that all fit together in the same world or universe. It's like a big puzzle that all goes together.
Now, the prefix "anti-" means "opposite of" or "against." So when someone talks about an "anticanon," they're talking about things that don't fit together or are even in direct opposition to the main story or world.
Think of it like you're building a big tower out of blocks. The "canon" blocks all fit together nicely and make a tall, sturdy tower. But the "anticanon" blocks don't fit well and might even make the tower wobbly or fall over.
Some people like to create their own anticanon stories or ideas that go against the main story, but others don't like it because it can be confusing or take away from the original story.
Does that make sense, little one?