There are three types of pages to choose from when creating a page in the CMS. Each has its unique purpose.
Internal:
Internal pages are your standard page within the CMS. Every page that you want to appear on your website should be set to internal. Internal pages offer you the freedom to add modules and completely structure your own page.
For information on setting up an Internal Page, check out this guide: Creating A New Page
External:
External pages are commonly used for cases when you want to have a button direct the user to a page no on the CMS.
For example, if you have a Hero banner on your homepage that you want to send the user to a specific blog post or maybe to your YouTube channel. Links that aren't part of your CMS and cant be chosen from the link dropdown field commonly used for buttons are shown below:

For information on setting up an External Page, check out this guide: Creating An External Page
No Link:
No link pages are used merely as folders within the CMS to store other pages within itself, usually for organisation.
A NoLink page requires two things:
- Page Name
- Page Filename
All other fields can be left blank

Once the NoLink page has been created, you can then start using it as a parent page for other pages as shown below:

Compared to other parent pages, the NoLink page will not show up in the URL of any child pages.
With a normal page it would change the URL to look something like this: testsite.com/parent/test
The NoLink page does not appear meaning the URL would stay as: testsite.com/test