Add notes about unique device IDs.

Author: dominicbetts

articles/iot-central/core/concepts-device-authentication.md

@@ -27,6 +27,8 @@ This article describes the following device authentication options:
 - [SAS enrollment group](#sas-enrollment-group)
 - [Individual enrollment](#individual-enrollment)
 
+Each of these authentication options requires that each device has a unique device ID. The device ID is a unique identifier for the device that you use to manage the device in your IoT Central application.
+
 ## X.509 enrollment group
 
 In a production environment, using X.509 certificates is the recommended device authentication mechanism for IoT Central. To learn more, see [Device Authentication using X.509 CA Certificates](../../iot-hub/iot-hub-x509ca-overview.md).
@@ -68,6 +70,9 @@ To connect a device with device SAS token to your application:
     az iot central device compute-device-key --primary-key <enrollment group primary key> --device-id <device ID>
     ```
 
+    > [!TIP]
+    > Each device that connects to your IoT Central application must have a unique device ID. The previous command generates a unique token for each device.
+
 1. Use the generated device token when the device connects to your IoT Central application.
 
 > [!NOTE]

articles/iot-central/core/overview-iot-central-developer.md

@@ -3,7 +3,7 @@ title: Device connectivity guide
 description: This guide describes how IoT devices connect to and communicate with your IoT Central application. The article describes telemetry, properties, and commands.
 author: dominicbetts
 ms.author: dobett
-ms.date: 03/01/2024
+ms.date: 10/21/2024
 ms.topic: conceptual
 ms.service: azure-iot-central
 services: iot-central
@@ -56,7 +56,7 @@ As you connect a device to IoT Central, it goes through the following stages: _r
 
 ### Register a device
 
-When you register a device with IoT Central, you tell IoT Central the ID of a device that you want to connect to the application. Optionally at this stage, you can assign the device to a [device template](concepts-device-templates.md) that declares the capabilities of the device to your application.
+When you register a device with IoT Central, you tell IoT Central the unique ID of the device that you want to connect to the application. Optionally at this stage, you can assign the device to a [device template](concepts-device-templates.md) that declares the capabilities of the device to your application.
 
 > [!TIP]
 > A device ID can contain letters, numbers, and the `-` character.