found this mini guide on androidforums.
When you root the phone you need to make sure you install busybox. After words verify your if you have root set-up correctly with root check basic by jrummy on Google play. If everything looks OK download terminal emulator from Google play. Once installed type "su". You should go from $su to #su on the next line. This means you have root access. If any additional info appears like "permission denied" or a long set of errors then the root is not set up properly. The solution is your system is not mounted as writable. There are a number of ways to mount the system as writable. The spimplest way is to download "es file explorer v1.5 (cupcake edition). This is an older version is es file explorer. Once installed go to setting scroll down to root section put a check in root devices and check mount system as writable. Reboot and problem fixed. Now this all depends if you followed the original root instructions properly.
Below Answer found on xda forum maybe helpfull.
"Busybox allows you or programs to perform actions on your phone using Linux (copied from Unix) commands. Android is basically a specialized Linux OS with a Java compatible (Dalvik) machine for running programs. The Android kernel is a modified version of the Linux kernel (that is why the Android kernel must always be open source). Busybox gives functionality to your phone that it does not have without it. Many programs, especially root programs such as Titanium Backup, require busybox to perform the functions of the program. Without busybox installed your phone is much more limited in what it can do".
Don’t have an account yet? Register yourself now and be a part of our community!
