Where is the course structure information coming from and how do I edit it?

I have set up three units:
What is Distance/Accuracy?
Distance/Accuracy Court
Distance/Accuracy Field

Yet, the Course Structure looks like this:
Distance/Accuracy Court
(tab) Untitled Page
(tab) Distance/Accuracy Field

I am really confused. Why is the Course Structure not identical to the Units I have created. And, where is the Course Structure info coming from and how do I edit it?

TIA

Peter