The Future plugin stands-in for a page about to be created. When one links to a non-existant page a temporary (ghost) page is created containing the Future plugin. The Future plugin creates new pages much like the Factory plugin creates new story items.
Template menu choices.
The Future plugin offers to make the temporary (ghost) page into a new real and blank page.
The Future plugin will offer to make a new page based on a template if any templates exist within the current site. A template is a page who's title ends with the word "Template".
Factory plugins can be configured with a "prompt" field in their json representation. Such prompts make a template serve the purpose of typical forms. Downstream form processing can look for items of a specific id to know that they contain answers to specific prompts.
A Twin (or sister) page is one on another site that shares the same name (slug) as a desired page.
A link will look in a few specific places for a page. If it isn't located where expected the Future plugin may find other locations by examining the current neighborhood sitemaps for a page by the same name.
When a twin has been located, one can review the page and possibly fork it to avoid this choice in the future.