Well Randy that is almost a philosophical question
When you do Leveling, you ensure that your resources are not overallocated.
The leveling process looks at the availablility of a resource and the
allocated time for the resource , and spreads the allocated time so that the
resource is not overallocated or has no unwanted gaps within a Project ( or
organisation, should you use Project Server ).
Leveling is a great tool, but can also be "a beast" if you dont know what
you are doing. The result of leveling can be influenced by many differnt
settings starting from Consrtain settings, calendar settings through to task
priority settings.
When I started with leveling I was simply "playing" with it and trying out
different things. One tip I can give you, dont use automated leveling, use
manual leveling. It gives you better control over what has happenend.
Please let me know if you have any additional questions in regards to
leveling. I know that it can look overwhelming when you start with it
Hope this helps