WSDL is not a method in itself for actually generating the client code, though. It's simply a (barely) machine readable description of the API from which clients decide how to deal with it.
EDIT: Since I was down-voted for whatever reason, I'd like to rephrase. WSDL is a standardized language for defining web services. It's not a tool in itself for generating client code, and what I said was meant to point out that that's the obvious difference between this and WSDL. A description written in WSDL can both be used to generate client APIs and skeleton code for the server itself, but isn't the generator itself, just like C isn't gcc.
