The "Additional Pages" works the same as your "Products & Services".
You will be able to add pages to your website and then allocate them to groups.
This is useful for the companies who have to seperate categories of items they offer to their clients.
The "Additional Pages" module will only appear as a link on your website menu once you have added a page to it.
(See "Products and Services" under the "Website Content" category for further help.)