BeNicer is a graphical interface to the UNIX 'renice' command. Renice let's you (system willing) change the priority of any process through the 'Nice' process attribute.
In UNIX the priority of a process determines the amount of CPU time it will get. When a process is launched it is assigned a priority by the system. Its starting 'nice' value is always zero. Changing your nice value is a way to make a suggestion to the system that the priority of a particular process be raised or lowered. The nice value can be set to anything from -20 to 20. Lowering its Nice level increases it's priority. Think of it as making the process 'more nice' (1 to 20) or 'less nice' (-1 to -20) to the other processes.
If you aren't sure what renice does, please go to your Terminal application and type "man renice" before using this script. This script is intended to be used by those that know what all these terms mean, but want a quicker way to do it.