According to a website, it describes how Earth's outer shell is divided into several plates that "glide over the mantle (which is the rocky inner layer)"
So, basically, it's talking about how the Earth's crust is structured.
Definition: a theory that is describing (or explaining) the structure of Earth's crust
There is no question to what you are saying. If you would lie this answered please first find what you need the answer to then ask.