PHP and SOAP newbie questions

I recently got handed a project that requires me to use PHP to talk to a WSDL SOAP service. I'm not new to PHP but I am new to SOAP. I have the basic idea of how SOAP works but still have a few questions I am hoping you all can answer for me. Which library would be better to use? NuSOAP or PEAR's SOAP library? Someone else is writing the WSDLs that I need to access. Does this mean that I just have to use a SOAP client to access the information or would I need to make a SOAP server? I guess what I'm asking is what is the difference between a SOAP client and a SOAP server? Lastly, do you all know of any good online tutorials I could check out that google may not suggest? Thanks! Jay