This might be a little confusing, but there were actually 4 releases of Windows 3.1x:
Windows 3.1 - First release, shown on previous page.
Windows 3.1 for Workgroups - Windows 3.1 packaged with real mode networking software and some extra utilities.
Windows 3.11 - Same as Windows 3.1 but with a few updated files. Made available as a patch to Windows 3.1 and on disks.
Windows 3.11 For Workgroups - (Shown here) Windows 3.1 plus core updates plus protected mode networking and extra utilities.

In order for Windows 3.1 to use networking, a DOS NIC driver, protocol, and client software had to be provided. As networking software became extremely feature rich, the size of the client software resident in the real-mode (640k) portion of RAM grew to to the point that many applications would not run due insufficient free real-mode RAM.

Windows For Workgroups solves this problem by adding protected mode network support. Rather than loading drivers in to the 640K segment, the Microsoft Windows Network software loads in the form of  ".386" files (AKA VxD files).

The downside to this is that when you exit to DOS, all networking support disappears.

This screen shot shows the network configuration control panel.

The first option is the type of network that is being used. This allows you to select support for third party DOS based networking system (they can not be used at the same time as the Windows Network), but in this case the Windows Network is selected, enabling the other options.

The second option allows you to share files and printers with other users on the network In other words, it can act as a print or file SERVER. This is something that is rarely seen in  DOS based networking systems, and traditionally costs megabucks in server licenses. The sharing dialog is open in this picture.

The last option is a list of network drivers and protocols. This may include a network card and/or Remote Access Server dial-up. Windows for Workgroups includes the NetBeui and IPX/SPX protocols. TCP/IP is available separately. RAS in Windows 3.11 is limited to the NetBeui protocol.

Windows for Workgoups connecting to a remote share. The connection dialog presents a list of all computers on the network with Windows compatible file sharing. Each share must be mapped to a drive letter, limiting the number of shares that may be in use at any one time. Windows for Workgroups is also limited to short "8.3" style filename.

Local folders can be shared though the File Manager. Once a folder is shared, a hand appears underneath the folder icon to indicate that it is shared.

This is the Remote Access dial-up application. It will connect to a remote computer running Windows NT RAS Server, or Windows 95/98 with the Dial-up server. Because it only supports the NetBeui protocol, it will not connect you to the Internet.

Windows For Workgroups also included several application to take advantage of the built-in networking system.

One of these applications is Microsoft Mail. It connects to a "PostOffice", which is a simple file share on a remote computer with user accounts and mail folders, and users can send and receive messages to and from other users in this Post Office.

Schedule Plus is a scheduling application that can be used as a stand-alone scheduler, or with a Post Office to share scheduling information.

The Microsoft At Work Fax allows users to send faxes using a local fax modem or to connect to a network fax server.

Microsoft Hearts is a card game that multiple players can play over a network.

The best part of Windows 3.x :)