Art is a
collection so as News, Mail and so
Links can be arranged in a
hierarchy of collections.
The set of all those collections
seen in the picture on the left hand side (Search, Mail, News, Art and so
on) is also called a collection named "NotJustbrowsing".
This collection may be representing
a "Book", "Notes" a "Photo Album" or just a collection. This collection of
collections reside in the Shelf and can be opened by double clicking left mouse