This version is an upgrade for Windows 3.0 users (and includes both Windows 3.1 and Windows 3.1 for Workgroups Add-on).
A Winsock package was required to support TCP/IP networking in Windows 3.x. Usually third-party packages were used, but in August 1994 Microsoft released an add-on package (codenamed Wolverine) which provided limited TCP/IP support in Windows for Workgroups 3.11.
Limited compatibility with the (then-new) 32-bit Windows API used by Windows NT was provided by another add-on package, Win32s. There was a rumor that Microsoft didn't want to increment any mainstream Windows 3.1x version to something like "Windows 3.2" because it could be scrambled with the Win32 API or otherwise distract consumers from upgrading to some 'real 32-bit OS' like the then-upcoming Windows 95 was. In fact, only for the limited Chinese market did Microsoft release a true Windows 3.2 version (see Windows 3.2 section).
Windows 3.x was eventually superseded by Windows 95 and later versions which integrated the MS-DOS and Windows components into a single product.