All Calendars is a single, consolidated super calendar which appears automatically on your dashboard as soon as you have access to more than one calendar.
You can access all posts from all calendars in All Calendars:
Here is a list of actions you can do from All Calendars View:
Access List view
Access Calendar View
Select a Default View (List or Calendar) for All Calendars in Settings.
Feel free to check out the Flash Webinar about Content Views here.