Windows NT, or Windows "New Technology", is a server operating system produced by Microsoft Corporation. The acronym "WNT" is clearly a pun on "VMS" (obtained by shifting each letter one position in alphabetical order).
It was originally based on OS/2, which was a joint project between Microsoft and IBM. The deal fell apart, and IBM continued to market OS/2 while Microsoft renamed their version to NT.
As NT enjoyed more success than OS/2, some critics of Microsoft suggest they used their large control of the software market to force their product onto consumers' hardware over their new competitors' product.