Here is my de facto standard reference on WDSL styles; bookmark it! When I first started writing Web Services I never knew their were 2 styles and 2 uses, or even that there was a style. As I gradually learned more about WSDLs it was difficult to find a good explanation of the different combinations. This article, written by Russel Butek on IBM developerWorks, explains how you determine which combination of style and use to choose. He provides advantages and disadvantages of each and shows WSDL and SOAP messages for each combination.
Overall when creating a Web Service you have 4 style/use options:
Please read this article if you are unfamiliar with the different styles and uses. In general the most common style used is document/literal wrapped with document/literal in second. Most newer SOAP Stacks actually don't support RPC anymore; for examlpe cxf (aka xfire) and axis2.