Any page title that ends in the word `Template` will be offered as a template when you create a new page.
For example, this page is itself a template. If you click on This Page Does Not Exist, you'll see the following:
Click to enlarge
Note that everything in the template is copied into the new page, so this page is a pretty useless as an actual template. Typically, you'll have an empty page with just structure, like:
### Incoming Links ### Content ### Outgoing Links
... or, using the PageFold Factory (About PageFold Plugin):
Incoming Links
Content
Outgoing Links