What is Superuser apk
Super user apk Grants and manages Superuser rights for your smartphone. The application dose require that you have rooted or have a custom recovery image on your smartphone for this to work correctly. If you have then you can download the Superuser apk file from the google play store link below.
Superuser apk rooting
Rooting your GS4Active gives you control over every aspects of your phone. After rooting your android phone install this application. You can then grant and manage Superuser rights to your galaxy s4 active. Superuser apk can not be uninstalled if it has been installed within your ROM or root. there is also no installation option as you have installed it within the /system/app,
The only way for an application to be placed in /system/app is via a rooting process (which usually installs Superuser), or by remounting the system partition as read/write and manually transferring that location.