What does "push notification" typically refer to in Webex Calling?

In the context of Webex Calling, "push notification" primarily refers to an alert sent to users when they receive a call. This functionality is crucial as it ensures that users are immediately informed of incoming calls, enhancing the communication experience. Push notifications facilitate timely responses and help users manage their calls more effectively. They are designed to work in real-time, meaning that users can stay connected and responsive even when they are not actively using the app.

The other options, while relevant in different contexts of communication or system management, do not align with the typical usage of push notifications in Webex Calling. System maintenance alerts, billing updates, and usage summaries are important, but they are generally communicated through different channels, such as email or app notifications of a non-push nature. Thus, option A correctly captures the essence of what push notifications are intended for within the framework of Webex Calling.