Permanent groups are maintained by EndNote and cannot be renamed or deleted. The permanent groups are:
All References: This displays all of the references in the current library. If you highlight a subset of references in this group and then display only those selected references, the name of the group changes to Showing References. The status line along the bottom of the window will always tell you how may references you are viewing plus the total number of references in the library.
Unfiled: This group contains those references that are not part of a custom group (and optionally not part of a smart group). Right- Control +click on Unfiled to display a context-sensitive menu and toggle the setting Exclude Smart Groups in Unfiled / Include Smart Groups in Unfiled.
Trash: This group contains the references you have removed from the library by highlighting references and selecting Move References to Trash from the References menu. While the references are officially no longer in your library (they will not appear in any other group or reference list, they are not included in your reference count, and they cannot be searched or cited), they are not completely deleted until you select Empty Trash in the References menu. Until you select Empty Trash, you can still drag references from the Trash group back to your active library.