TileSet / TileMap Terrains - What Does the Middle or Center Bit Do?

Godot Version

4.2

Question

Hi all, I am trying to figure out in the TileSet Terrains. When you’re painting bits onto your map. What is the purpose of the Center/Middle bit? I can’t seem to figure out what the difference is between turning it on vs off when matching sides, corners, or both. Is it for a more advanced system? Is it if you’re using multiple sets?

I don’t see it explained in the documentation section on tileset terrains either, and I can’t seem to figure out the difference with experimenting either.