The Instances tab provides a broad visibility of your environment. SQL Elements displays on this section all available instances in the following categories:

These three categories let you see all your managed instances, if you do not have the auto-registration option enabled, you can decide which instances to register from the list of newly discovered, and which ones to ignore. By ignoring new instances, you remove them from the Discovered tab, so that it is easier to see new instances as they are discovered.