When one specific app keeps getting in your way
Blanket notification settings, like Do Not Disturb, silence everything at once, which is not always what you want -- often only one particular app is the actual problem, while everything else is fine as is. Adjusting notifications app by app lets you target exactly the source of the interruption without muting anything you actually rely on.
Category-level control depends on the app
Some apps split their notifications into separate channels -- comments, direct messages, promotions, and so on -- each with its own switch, so you can silence just one type without losing the rest. Apps that have not built out that structure only offer a single overall on/off switch, so how much control you get varies from app to app rather than being consistent across the board.
Frequently Asked Questions
Can I always fine-tune notifications by category?
Only for apps that have split their notifications into separate channels. Apps that have not done this only offer a single overall on/off toggle.
I only want notifications hidden on the lock screen, not turned off entirely.
On the same app notification settings screen, adjust the "Show on lock screen" option separately -- you keep getting the notifications, but their content stays hidden while the screen is locked.