Promoting your assets is a way of showcasing them on the homepage in a dedicated "Promoted Items" image strip.
The 'View All' link allows a user to see all assets that have been promoted by an administrator.
To promote an asset, simple check the 'Promoted Asset?' checkbox when editing an asset.
At this point you may also choose to set an expiry date (this is not mandatory by default), after which the asset would be removed from the 'Promoted Items' strip.
Users will only see assets that they have the relevant permission to see, whether they are Promoted or Featured.
There is a setting in Admin > Content > Featured > 'Update the featured asset visibility settings' that will allow you to set the Featured asset as 'visible' to all users of the system, regardless of the group permissions that would normally apply.