Novell NetWare
Novell Netware is a network operating system developed and maintained by Novell, Inc. It initially used cooperative multitasking to run as a server atop a Personal Computer, and the network protocols it used were based on the archetypal Xerox XNS protocol stack.
In the early to mid 1990s the NetWare platform was the most popular operating system dedicated to serving files over a Local area network (LAN). In the later half of the 1990s NetWare was eclipsed by the popularity of Microsoft Windows NT (now known as Windows Vista).
Since Novell has shifted its strategy and now embraces open source software, NetWare has been deprecated, in favor of Open Enterprise Server (OES). The latest (and most likely last) version of NetWare is v6.5, which is identical to OES-NetWare Kernel, Support Pack 2. (OES can run on top of a NetWare-based operating system or on a Linux-based operating system).
History
(note: for more information on Novell's history see the history section of the Novell article)
NetWare came about in answer to a brand new market in Computer networking: file sharing. A centralized NetWare server would be dedicated to sharing files over a LAN to other clients running their own client operating system (clients could be UNIX-based, DOS/Windows based, etc). This centralized model made backups easier, and the server could be made redundant to provide for hardware failure.
NetWare's Decline
As Microsoft's Windows Server based operating systems grew in popularity, NetWare saw a sharp decline in popularity. Novell has changed its strategy and bet the company on "Open Source"-based products, and its server architecture itself is now Linux based .