Back in 2016, Google announced a new feature that would let you receive messages from apps that you don't necessarily have installed on your device. For example, your friend could send you a message on Allo even if you didn't have the app installed on your Android phone. You could even reply to the Allo message natively through that notification, as if you had the app installed. It appears that Google Photos is the latest Google app to soon adopt the feature, as 9to5Google reports. Although the App Preview Messaging API is still in the preview stage, Google appears to be testing the...
Source: https://www.gsmarena.com/new_google_photos_notification_shows_a_preview_of_shared_photos-news-29505.php
