Google Analytics is a free analytics solution provided by Google, featuring several client-side APIs for data collection. This tag is used for the Collection protocol specifically for Android and iOS SDKs versions 4.
Google Analytics provides easy to use APIs and SDKs to send data to Google Analytics.
With the collection APIs and SDKs, you can measure how users interact with your content and marketing initiatives. Once implemented, you will be able to view user-interaction data within Google Analytics or through the Reporting APIs.
Android Google Analytics SDK v4 for Android - Getting Started
iOS SDK Google Analytics SDK for iOS v3 - Getting Started
You can use the SDK by using Google Play services SDK. This SDK can be downloaded from https://developer.android.com/google/play-services/index.html.