Q Why Learn about WSDL?
A WSDL documents tell you the specifics about an XML Web service. If you are building a client application, especially if your client is not using .NET as its platform, it is often invaluable to be able to look into a WSDL document and see how your programs can access the service's functionality. It is also important to have a very good understanding of WSDL if you should ever come across a situation that calls for the WSDL document to have to be hand altered, such as a situation where you wish to force clients to use one specific port and disallow the others.
Q Why is s always used as the namespace for simple data types?
A If you look at the definitions element of the Visual Studio .NETgenerated WSDL files, you will see that s is the name given to the XMLSchema namespace. This is the namespace that defines XML's common data types. The use of s is, of course, arbitrary and can be replaced with any other valid XML token.
Q WSDL seems very complicated. How do I create a document and not have errors?
A The odds are that you will never have to create WSDL documents by hand. Tools such as Visual Studio/ .NET create them for you. As stated previously, the purpose of learning WSDL is so that you can understand the documents when you encounter them and alter them if you absolutely need to.