"New Technology", "Next Technology", "Network Technology", "Not Today", "Nice Try", "New Tamagotchi"...
Who knows what NT really means? Some say that WNT—Windows NT—is a pun on VMS: if you shift each letter in VMS ahead one place, you get WNT. Similarly, NT is simply MS—Microsoft—shifted one letter. Such an explanations find favor among those who like the fact that HAL—from 2001—is IBM, each letter shifted back one. Whether such things were intended on the part of the developers, etc., is irrelevant; as have the explantions above for what NT means, such stories have managed to enter into a type of public "mythology."
The actual history behind Windows NT, what it is, and what it should be, is both more mundane and more interesting than attempts to decode two letters.
Windows NT owes its existence to the fact that IBM never meant the PC market to be what it has become. IBM, when it decided to create its first PC, did not believe much in "micro-computers"—small, desktop computers, todays PCs. Some say, it still doesn't (witness its abandoning of OS/2 ...). It licenced a weak, basic OS from Microsoft—DOS—to power the 250,000 or so PCs it planned to sell. However, pretty soon Intel's chips had outgrown old 16-bit DOS, and with Apple introducing the Macintosh, IBM and MS decided to create a 2nd generation operating system—OS/2. For several years, IBM and MS worked together, but in the late 80s, the two companies "divorced," and MS rebranded its next version of OS/2 as NT in 1990.
However, this is not (completely) the NT we have today. Back around 1988 (see the paper by Michael Podanoffsky), MS began work on NT. It was going to be everything DOS/Windows wasn't:
Microsoft envisioned the creation of Windows NT, a portable operating system capable of supporting multiprocessors, true preemptive multitasking, full 32-bit access, multithreading, shared memory, security and crash protection, among a host of other important features. DOS and 16-bit Windows would be supported as host environments. (Podanoffsky)
Much has been made about the "NT" in Windows NT; was it truly New Technology? Dave Cutler was the primary architect of both NT and Digital's VMS, and many see a connection (as mentioned above) between WNT and VMS. This factoid has been used for different purposes; some argue the VMS influence proves there is nothing "new" about NT; others, particularly those on the NT side in the UNIX vs. NT debate, argue that this makes NT the logical and natural successor of VMS. What we can safely say is: NT and VMS shared certain developers. Furthermore, they shared some design and implementation features in common; then again, NT and UNIX solved certain problems in the same way, yet people don't claim NT is a UNIX clone.
Today, we have the antiquated NT 4.0, and Windows 2000 and XP, both "based on NT technology." For a while MS played with a port of NT to the PowerPC architecture, but that, like IBM's PowerPC OS/2 port, has been abandoned; a more well-maintained port of NT was made to the Alpha processor.
Windows NT is an awesome concept: 32-bit, multi-tasking, great protection (security and crash), and highly portable due to the fact that, like Mach (used in MkLinux, for example), NT has a micro-kernel architecture. NT has none of the annoying limitations of DOS, such as the 640K barrier. NT is much more powerful than Windows 95/98 or its predecessors. With greater multi-tasking and multi-threading, NT should be more responsive, efficient, and faster than other MS offerings, and perhaps even more so than Unix.
Microsoft marketed NT, and then Windows 2000, primarily toward the server and workstation markets, not yet bringing it into the home; Windows XP was the first NT-based OS to be aimed at home users. It supports OpenGL, and numerous high-end applications, as well as standard 32-bit Windows applications, run on NT-based systems. Furthermore, NT 4.0 and 2000 had the same user interface as Windows 95/98, and XP's is simiar (more eye-candy).
Windows 2000 provides a more stable computing environment than Windows 95/98.
One word: WindoesN'T.
Many who have worked with NT have experienced the painful BSOD—"Blue Screen of Death." NT's famed "uncrashability"—its memory protection, for example—simply isn't all that it claims to be. Trusting mission-critical tasks to NT, and even using NT as a server, is just asking for trouble. Things improved, however, with 2000 and XP. At the same time, if you install 2000 or XP, also expect to install a variety of Service Packs (some of which have a history of causing more damage than good).
Do not attempt to run 2000 or XP on older machines; you will want lots of memory and a fast processor. They are resource hogs par excellance. NT-based machines are only for 32-bit Windows applications; 16-bit Windows applications and DOS programs need not apply; if you have old DOS games, stick with DOS or Windows 95/98, or use an emulator.
In addition, NT-based OSes are not an inexpensive option. NT came in two flavors: Workstation and Server; similar licencing exists for 2000 and XP. Furthermore, Microsoft looks to be moving to a per-year licencing scheme; you won't buy it once and be happy, instead you'll have to "resubscribe" every year.
If you have a recent PC and 32-bit Windows software you want to run, Windows 2000 or XP make a better choice than Windows 95/98/ME—they are, under most conditions, more stable and powerful, and the interface is practically identical. There is no reason to install NT 4.0 or before, except for reasons of curiosity.
However, that is the only reason, except fear of the unknown, to choose Windows. In comparison: Linux and *BSD are free, as well as more powerful (and stable!). If you are looking to buy a new computer, Apple's OS X makes a great option on desktops and laptops. For older PCs, even IBM's OS/2, while not quite as robust as NT (should be), provides both a stable desktop and server option.
Below you will find a few links to NT-related pages: