A Device subgroup is an optional way to provide hierarchical organization for data items provided by the OPC Server.
Subgroup are similar to Windows Explorer Drive:\Folder\File organization.
Example
Creating a Subgroup:
Right click on the name of the device in the Device Pane and select New Group…
Enter a Name
Enter the name of the Subgroup in the Group dialog box
The Name can be up to 32 characters in length
The Name must not contain dots ("." Periods)
Click the OK button.
Also See: Menu Bar -> Add New Group