Why do apps send notifications?

Answer: Tell people about messages and reminders as they arrive

Tell people about messages and reminders as they arrive ✓ — Correct! Notifications exist to deliver timely information a person might act on—new messages, reminders, delivery updates—without making them open the app first. Apps register with a push service that keeps a connection open, so the service can send an alert even when the app is not running. Users can then choose which apps are allowed to send these alerts in system settings.

Collect location data so ads can target the user — Wrong. Location tracking can be a separate permission some apps request, so it is easy to confuse with notifications. But the notification itself is a message channel; it does not need your location to tell you that a message arrived. Mixing the two would make an ad-targeting feature sound like the reason every notification exists.

Keep the app running in the background so it opens faster — Wrong. Keeping an app alive in the background can make it reopen faster, but that is an app performance choice, not the purpose of a notification. Notifications are delivered through a push service and can arrive without the app's process staying in memory. The alert is the point; memory use is an implementation detail.