Integrated Windows Authentication is a term associated with Microsoft products that refers to the SPNEGO, Kerberos, and NTLM authentication protocols. Use tag with Windows authentication generally; though it might be best to use one of the more protocol-specific tags (such as Kerberos or NTLM) if the protocol being used is known.
Integrated Windows Authentication (iwa) is a term associated with Microsoft products that refers to the spnego, kerberos, and ntlm authentication protocols with respect to sspi functionality introduced with Microsoft Windows 2000 and included with later Windows NT-based operating systems. The term is used more commonly for the automatically authenticated connections between Microsoft Internet Information Services (iis), internet-explorer, and other active-directory aware applications.
IWA is also known by several names like HTTP Negotiate authentication, NT Authentication, NTLM Authentication, Domain authentication, Windows Integrated Authentication, Windows NT Challenge/Response authentication, or simply Windows Authentication.
Source: http://en.wikipedia.org/wiki/Integrated_Windows_Authentication
