understand groups

Author: v-thepet

articles/iot-hub-device-update/device-update-groups.md

@@ -1,81 +1,76 @@
 ---
-title: Understand Device Update for Azure IoT Hub device groups
-description: Understand how device groups are used.
+title: Azure Device Update for IoT Hub device groups
+description: Understand Azure Device Update for IoT Hub user-assigned and default device groups and subgroups based on device classes.
 author: aysancag
 ms.author: aysancag
-ms.date: 2/09/2021
+ms.date: 01/07/2025
 ms.topic: concept-article
 ms.service: azure-iot-hub
 ms.subservice: device-update
 ---
 
-# Device groups
+# Azure Device Update for IoT Hub device groups
 
-A device group is a collection of devices. Device groups provide a way to scale deployments to many devices. Each device belongs to exactly one device group at a time.
+An Azure Device Update for IoT Hub device group is a collection of IoT devices that provides a way to target deployments. Any device that has the Device Update agent installed and provisioned belongs to a device group.
 
-You may choose to create multiple device groups to organize your devices. For example, Contoso might use the "Flighting" device group for the devices in its test laboratory and the "Evaluation" device group for the devices that its field team uses in the operations center. Further, Contoso might choose to group their production devices based on their geographic regions, so that they can update devices on a schedule that aligns with their regional timezones.
+You can use the default device group that Device Update assigns, or you can create and assign multiple device groups to organize your devices. For example, the Contoso organization might use a "Flighting" device group for the devices in its test laboratory and the "Evaluation" device group for the devices its field team uses in the operations center. Contoso might also choose to group their production devices based on geographic regions, so they can update devices on a schedule that aligns with their regional timezones.
 
-## Create device groups using device or module twin tags
+## User-defined device groups
 
-Tags enable users to group devices. Devices need to have a ADUGroup key and a value in their device or module twin to allow them to be grouped.
-
-### Device or module twin tag format
+You use *tags* to group devices. An `ADUGroup` key with a user-defined value in the `"tags"` section of the device twin or module twin specifies a user-defined device group.
 
 ```json
 "tags": {
   "ADUGroup": "<CustomTagValue>"
 }
 ```
 
-## Default device group
+## Default device groups
+
+Devices that have the Device Update agent installed and provisioned but don't have an `ADUGroup` tag in their device or module twins are automatically added to a `default` group based on their device class. Devices with the same device class are grouped together in the default groups, also called *system-assigned groups*.
+
+Users can't delete or recreate default groups, change their definitions, or add or remove devices from default groups manually. Default group names have the format `Default-<deviceClassID>`, and are reserved within an IoT solution.
+
+The default groups help reduce the overhead of tagging and grouping devices, to make it easier to deploy updates to untagged devices. All deployment features that are available for user-defined groups are also available for default, system-assigned groups.
 
-Any device that has the Device Update agent installed and provisioned, but doesn't have the ADUGroup tag added to its device or module twin, will be added to a default group. Default groups, also called system-assigned groups, help reduce the overhead of tagging and grouping devices, so customers can easily deploy updates to them. Default groups can't be deleted or re-created by customers. Customers can't change the definition or add/remove devices from a default group manually. Devices with the same device class are grouped together in a default group. Default group names are reserved within an IOT solution. Default groups will be named in the format `Default-<deviceClassID>`. All deployment features that are available for user-defined groups are also available for default, system-assigned groups.
+## Example device group assignments
 
-For example consider the devices with their device twin tags below:
+For the Contoso example, consider four devices with the following device twins:
 
 ```json
 "deviceId": "Device1",
 "tags": {
-  "ADUGroup": "Group1"
+  "ADUGroup": "Flighting"
 }
 ```
 
 ```json
 "deviceId": "Device2",
 "tags": {
-  "ADUGroup": "Group1"
+  "ADUGroup": "Flighting"
 }
 ```
 
 ```json
 "deviceId": "Device3",
 "tags": {
-  "ADUGroup": "Group2"
+  "ADUGroup": "Evaluation"
 }
 ```
 
 ```json
 "deviceId": "Device4",
 ```
 
-Below are the devices and the possible groups that can be created for them.
-
-| Device  | Group                         |
-|---------|-------------------------------|
-| Device1 | Group1                        |
-| Device2 | Group1                        |
-| Device3 | Group2                        |
-| Device4 | DefaultGroup                  |
-
+Device1 and Device2 are both assigned to the "Flighting" device group. Device3 is assigned to the "Evaluation" device group. Device4 has no tags so is assigned to the default device group.
 
 ## Subgroups
 
-All user-created groups as well as default groups are automatically sub-categorized into one or more subgroups to allow administrators to manage heterogeneous devices in an organized and efficient manner, by providing a way to perform updates on a set of devices that share compatibility properties. Each device class within a group maps to one subgroup. Devices are added to a subgroup based on their compatibility properties and the Device Update PnP model ID, which together comprise a device class. 
-
-A group can have one or more best available update, one for each subgroup it contains. 
+Device Update automatically categorizes all user-created and default groups into one or more subgroups. Subgroups help administrators manage heterogeneous devices in an organized and efficient manner by updating sets of devices that share compatibility properties.
 
-[Learn more](./device-update-configuration-file.md) about setting compatibility properties on the Device Update agent
+Device Update adds devices to subgroups based on their compatibility properties and the Device Update PnP model ID, which together comprise a device class. Each device class within a group maps to one subgroup. A group can have one or more best available updates, one for each of its subgroups.
 
-## Next steps
+## Related content
 
-[Create a device group](./create-update-group.md)
+- To learn how to create, view, and delete device group tags and assign and remove devices from groups, see [Manage device groups](create-update-group.md).
+- For more information about about setting compatibility properties on the Device Update agent, see [Device Update configuration file](device-update-configuration-file.md).