Rita El Khoury, writing for Android Police:
Android 8.0 Oreo introduced one cool feature for app notifications: channels. Since not all notifications are created equal, even if they come from the same app, this would allow you to choose how different types of notifications appear, sound, and vibrate, or not, on your phone.
Being able to have fine grain control of how an app like WhatsApp handles notifications is a huge deal. One of the unsung heroes of Android Oreo.