The subscriber rewards control what commands, if any, are reward to users when they subscribe to your channel.
To enable the subscriber rewards you must toggle them on.
You can see if subscriber rewards are currently enabled by the overlay icons in the navigation menu and window title bar. When enabled the overlay icon is shown, e.g.
When disabled, the icon will be used instead.
The general tab of the subscriber reward screen controls what if anything is rewarded when you get a new subscriber or an existing subscriber re-subscribes.
The notification tab of the subscriber reward screen controls what if anything is sent to chat when you get a new subscriber.