Page enhancements allow you to add links to other pages within your app, effectively "jumping" the end user to a specific page.
The Tracking Name is an arbitrary name, not visible to end users, that auto-fills future instances of this same page jump. For example, if you are adding a jump to your cover story in the Page # field, you might use "Cover Story" for the Tracking Name. In the future, you can just type the first few letters of "Cover Story" and the editor will auto-fill the URL for you.
No Repeat simply means that this page jump will not repeat in the same place on future pages. If you would like it to, click it for a drop-down menu that allows you to select from the options "All Pages," "All Except," and "Every Other" (each taking effect from the current page forward, not in reverse).