Rooting is a process allowing users of mobile phones, tablet PCs, and other devices running the Android operating system to attain privileged control (known as “root access”) within Android’s subsystem. Rooting is often performed with the goal of overcoming limitations that carriers and hardware manufacturers put on some devices, resulting in the ability to alter or replace system applications and settings, run specialized apps that require administrator-level permissions.
These root privileges are needed for a few options within avast! Mobile Security - like the Firewall.
Please consult http://en.wikipedia.org/wiki/Rooting_(Android_OS) for more information about rooted devices.
to find out how to root your device please perform an internet search:
root xda
you’ll find good step-by-step-rooting-guides within the XDA developers forum. be aware that you will loose your warranty if you root the device.