"carpet" of bookmarks and sessions ("inside" tabs and windows)

This may be purely linguistical, but what are exactly sessions? This is one
of the features in which Opera was unique. Each session is a group of web
pages, it can be auto-saved (useful after a crash and for consistency of
information) or it can be saved by users. But looking at it, why is a
session different from a group of webpages inside a "carpet" of the
bookmarks library? Isn't that redundant?

Firefox has a feature that (as of this writting) isn't implemented in Opera:
save all open webpages (the tabs in a window). Isn't this basically the same
as saving a session? btw, Firefox cann't manually save sessions (without
extensions) it just auto-saves sessions (that opens after a crash).

Sessions and Bookmarks "carpets" can be one... they may even be called in
another way (imagine an auto-saved or last-read session in the
"bookmarks-menu"). If this session has a second level (another "carpet"),
then it may represent a new window (the bookmarks in the top-level are the
"top-window", the rest opens "as tabs inside a new window"). "carpets"
(capable of more than 2 levels) may still be used along with sessions. But
if it's so, then does the session-carpet should behave as a special carpet
(with 2 levels limit)? Or should it be "converted on-the-go" to a regular
carpet if users ad a new level (that cann't be opened inside a window...
unless we cut the window in two jeje)?

Maybe this is overthinking, but web-browsers can be streamlined. Why not
call the Bookmarks-menu WebSites or WebPages? Is bookmarks clear enough (for
first users, old-time users are "comfortable" because of habits). And now
that we're at it, why a "file" menu in a web-browser? Shouldn't some "file"
functions be in the website menu (like Print)? And why "save webpage" is in
"file-menu" and not in "edit-menu" near copy, paste, delete?

This is not only about web-browsers but someone mentioned in a web-forum (
www.linuxquestions.org if I recall correctly ) about naming windows in a
different way, like boxes. Windows (boxes?), Files (information?), Carpets
(lists?), and other desktop-names aren't clear at all in most cases, IMO.

--
http://www.zensui.org