Nautilus is the official file manager

File manager

A file manager or file browser is a computer program that provides a user interface to work with file systems. The most common operations performed on files or groups of files are: create, open, edit, view, print, play, rename, move, copy, delete, search/find, and modify file attributes, properties...

 for the GNOME

GNOME

GNOME is a desktop environment and graphical user interface that runs on top of a computer operating system. It is composed entirely of free and open source software...

 desktop. The name is a play on words, evoking the shell of a nautilus

Nautilus

Nautilus is the common name of marine creatures of cephalopod family Nautilidae, the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. It comprises six living species in two genera, the type of which is the genus Nautilus...

 to represent an operating system shell

Shell (computing)

A shell is a piece of software that provides an interface for users of an operating system which provides access to the services of a kernel. However, the term is also applied very loosely to applications and may include any software that is "built around" a particular component, such as web...

. Nautilus replaced Midnight Commander

Midnight Commander

GNU Midnight Commander is a free cross-platform orthodox file manager and a clone of Norton Commander originally created by Miguel de Icaza.Midnight Commander is licensed under the terms of the GNU General Public License.-Design:...

 in GNOME 1.4 and was the default from version 2.0 onwards.

Nautilus was the flagship product of the now-defunct Eazel

Eazel

Eazel was a software company based in Mountain View, California from 1999 to 2001.The enterprise was staffed with former employees of Apple Computer, Netscape, Be Inc., Linuxcare, Microsoft, Red Hat and Sun Microsystems, among others. Mike Boich was CEO; Bud Tribble was VP of Engineering; Andy...

 Inc. Released under the terms of the GNU Lesser General Public License

GNU Lesser General Public License

The GNU Lesser General Public License or LGPL is a free software license published by the Free Software Foundation . It was designed as a compromise between the strong-copyleft GNU General Public License or GPL and permissive licenses such as the BSD licenses and the MIT License...

, Nautilus is free software

Free software

Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...

.
Nautilus was first released in 2001 and development has continued ever since.