how is the price of an item determined for a given client

Hi,

I'm checking the table structure of BW http://www.sage.com/na/~/media/site/Sage%20BusinessWorks/Documents/BWGFormats_Final.pdf and I note that in the ARCustomer table there are two fields related to price PriceLevel and ICPriceLevel and I find that confusing. 

So basically , I have a very simple question, how is the price calculated for a given for a given customer?

Hope the question is clear.

Thank,

Ignacio