Okay kiddo, a vexilloid is just a fancy way of saying a flag or something that looks like a flag. You know those things that people wave around during parades or hang up on poles? That's a flag!
Now sometimes people make things that aren't exactly flags but kind of look like them. They might use the same colors or designs but it's not meant to be waved around like a regular flag. That's when they call it a vexilloid.
It's like when you draw a picture of a dog, but instead of using a pencil, you use crayons or markers. It's still a picture of a dog, but it looks a little different. Same thing with a vexilloid, it looks like a flag but it's made for a different purpose.