Adding webreference in a application

Dear friends,

This is the first question I am posting in this web site.. hope I will get the answer.

I just wanted to know the difference in adding a webrefence to an application., between http://www.localhost/Samplewebservice/Samplewebservice.asmx and http://www.localhost/Samplewebservice/Samplewebservice.asmx?wsdl

Thanks in advance,

Ram.