They talk about most of those in the book that comes with the TiVo.
Here is an example.
When Groups are on, shows are organized into folders, and a number in parentheses to the right
of each folder shows how many shows it contains. If you’ve recorded several episodes of the
same show, they can all be collected into a group.
To turn Groups on, press the red button on your TiVo remote (Groups are on by default).
Press it again to turn Groups off.
Even if Groups are turned off, you’ll see the Recently Deleted group at the bottom of the My
Shows list. Shows you delete go to the Recently Deleted group, where they remain until space is
needed for new recordings.
A show’s title may appear in more than one group, even though there is only one recording of
the show. For example, you might have several episodes of a show in that show’s group, and the
same titles in the HD Recordings group, which includes all shows recorded in HD. When you
delete a show in one group, the title also disappears from any other group.
When your shows are grouped, you can highlight the group name and press PLAY to play all of
the shows in the group in sequence, beginning with the oldest."