The following document explains the different options available for calendar event notifications using an iOS device (iPhone, iPad, or iPod Touch).
Apple iPhone Calendar uses the terms Alerts, Notifications and Reminders in different ways.
A reminder equates to what other applications call Tasks. On the iPhone these items exist in a separate application called Reminders .
There are two types of Notifications on the iPhone. There is a new iOS feature called Notifications enable by swiping downward from the top edge of the screen when in vertical orientation (the Notifications dropdown does not reorient if the iPhone is held in horizontal orientation). The settings for this feature are in iOS Settings and there is an item in it for iPhone Calendar that tells iOS to use this Notifications feature to display Alerts and meeting invitation notifications.
Alerts serve to call your attention to something. For iPhone Calendar an alert relates to a pending event. One sets an event's alert in the event's properties. Alert preferences are set in the iOS Settings application. To set options for Alerts:
Tap on the Mail... button at the top-left to return to the Mail, Contacts, Calendar display.