The GNOME FileManager.

Originally developed by Eazel, some Macintosh Finder developers that quit Apple during the era. Eazel were going to attempt to provide anywhere-in-the-world access to a constant desktop, and to that end needed a file manager. So they wrote Nautilus. It was adopted as the official GNOME FileManager (to replace gmc).

Eazel went bust, the staff all went back to Apple, and Nautilus is now developed mostly by the GNOME foundation and developers around the world.

See NautilusNotes for some, well, notes about Nautilus