Add FAQ's on notifications to backgrounded Android apps

Author: ashton-huxtable

src/connections/spec/native-mobile-spec.md

@@ -59,3 +59,15 @@ You can, but the sooner you switch to the spec'd events, the further back you'll
 ### How will I be able to take advantage of new campaign events?
 
 In the coming months, we'll be updating our mobile marketing destinations to automatically capture campaign events around attribution, deep linking, and push notifications. These events will go to [destinations](/docs/connections/destinations/), including [warehouses](/docs/connections/storage/catalog/).
+
+### Why don't Push Notification events reach Segment when my Android App is backgrounded?
+
+Android applications can't receive Push Notifications when the process is not running, and when apps are put into background the are eligible to have their Process killed when there is memory pressure. You can read more on Android processes and the [app lifecycle here](https://developer.android.com/guide/components/activities/process-lifecycle).
+
+At Segment, we track messages delivered to the application. So if the process has been killed for any reason, the messages will not be delivered. 
+
+### Why do Push Notifications work with Firebase Cloud Messaging when the app is backgrounded?
+
+Firebase Cloud Messaging (FCM) has it's own servers. When an FCM message is created and sent to a device, that message travels through FCM servers and is delivered to the device to the local FCM client that is part of Android OS. This FCM client is pretty much always running, even when the app is backgrounded. From there the FCM message is intended to be delivered to a local application. If the app process is running it will be delivered. If not, then a notification will be created that the user must tap that will start the App and deliver the FCM message.
+
+For more context on how this process works, you can see the Firebase documentation on the [FCM architecture here](https://firebase.google.com/docs/cloud-messaging/fcm-architecture).