Okay kiddo, imagine you have a drawing of a mountain with bumps and ridges that stick out. That's called a relief.
Now, imagine someone took that drawing and instead of making the bumps and ridges stick out, they pushed them IN instead. That's what we call an inverted relief.
It's like taking a photograph and flipping it upside down. The things that used to be up high are now down low, and the things that used to be down low are now up high.
It's kind of like a mirror image but turned a different way. Does that make sense, little one?