Back in the old days of feature phones (remember those?) we personalized ringtones a lot. Besides coolness, it helped to quickly differentiate the callers. This allowed a lot of granularity. It took an instant to recognize a ringtone, associate it with a specific caller, and triage the incoming call to decide whether to take it.
Then came smartphones with a new channel for requesting our attention, notifications. Recent Android versions added granularity to the notifications a specific app can issue. Now we can decide which notification channels we want.
The system feature that makes such granularity possible is notification channel management, covered in an article below.