Useful article on WSDL styles...

is here. Very good summary. An overview would be:

rpc-encoded: SOAP body has a child with the method name. Child elements of the method are type encoded e.g. with an xsi:type attribute. Not WS-I compliant.

rpc-literal: similar to rpc-encoded but the child elements don't have type attributes, which are probably overhead anyway, but means the message can't be validated.

document-encoded: is never used.

document-literal: no element inside the SOAP body which tells you which method to invoke. Maybe that's fine if you know what sort of content to expect, e.g. on a particular messaging channel, or URL.

document-literal-wrapped: variant of the above, but with a child element of the SOAP body to wrap the parameters to a method, which gives you an easy way to dispatch the method to a handler.