Leave unchanged if you are using the public Microsoft Azure cloud.
If you are using a private or other Azure cloud service, enter the authentification endpoint URL for that cloud.
You can get this information from the Azure portal.
Here's a list of commonly used values:
Azure China: https://login.chinacloudapi.cn/
Azure US Government: https://login.microsoftonline.com/
Azure Germany: https://login.microsoftonline.de/