When you create a web service or you want to study a web service which a third party provides to you, you may need to code a test program to test your web service. It may consume your time.
With Web Service Studio, you won't worry about how to make a test program for testing a web service. Web Service Studio invokes web methods interactively. You just provide a WSDL endpoint then click Get button to fetch the WSDL and displays the list of methods available. After that, you can choose any method and provide the required input parameters then click Invoke button to make the SOAP request to the server and receive the response with returned values.
Here is a picture for demo: