What isa difference between windows2000/2003 and nt

Windows NT was a series of windows operating systems for networks and servers
Windows 2000 was the last operating system based on NT
Microsoft used to have a line of operating systems for home use which were 3.1, 95, 98, ME
They did not have the stability, compatibility and network features that were required in buiseness environments so Microsoft had a NT line (interestingly the first NT operating systems were based around OS/2 which was a joint project between IBM and mirosoft).
Since the millennium computer use in homes has gone to people using networks and always on internet connections so Microsoft didn't need separate products lines. But the technology that was in early NT operating systems has stuck: the filesystem now used on nerely every windows computer NTFS was introduced with the first version of windows NT as NTFS version 1.0 now its at version 3.1, windows XP is based round a NT kernel (the barebones of the operating system) so its also known as NT 5.1 (64bit version and 2003 server are NT 5.2)

Windows server 2003 is an operating system specifically designed for servers (before that was windows 2000 server) it has tools and services especially for servers

There are many version of server2003 which have different specialisations depending on what the server its installed on is for, so you can get web edition, datacentre, storage server...

Latest version of windows server is 2008 (this is NT 6.0 like vista)