The Notification plugin is designed to be easy to setup even for beginner users. If you are familiar with WordPress dashboard you'll find the Notification plugin very intuitive.
It has a bunch of predefined Triggers you can use and which will work out of the box.
But the plugin is not limited to "clicky-click" in WordPress dashboard. It's very extensible and developers can use it as a framework in their own plugins or themes.
This opens a lot of possibilities. Developers can do their thing and the users can still use the easy and unified interface to edit the Notifications.
Example? You could send a pidgeon to your friend when someone clicks a button on your website. But you'd have to find the API for pidgeon submission first