Shared templates are blank sides that you are customizing in various ways. These pages will serve as template pages for the purpose of reusing often in various courses. The content of the text and image will change, but the format will pretty much stay the same. By saving these pages as 'Shared Templates', you will have a whole section dedicated to easy access to various types of page templates which you can copy in your course with a single click.
How to Create Shared Templates
After you have customized your blank slide the way that you want. In order to create this page as a shared template, make sure you renamed the page to something proper, then click on the page menu dropdown and click on the options button on the right of the page name.
In the menu parameters, click on 'Save as a new slide template'. Click on yes to confirm and this is it. From now on, whenever you access the 'Shared Templates' section in the 'Add Page' Menu, you will see your page displayed there.
From there you can simply click on the page, name it, and it will create a copy of it in the course that you are working on. You can then further modify the page to fit the current course, but you started from a template that helped you save a lot of time and effort. If you need to delete a shared template, simply click on the button in the bottom right of the thumbnail as shown in the image and you will be able to delete that page from the shared templates folder.