How does Test Complete interact with WatiN

Hi all,

I am an amateur in test complete and wanted to know how does it interact with watiN. I have scripts that call watiN functions. I know that watiN is used for web automation testing. I have a web application that is built in java. I have a windows application that is in .net. I have to use the site ID from web application to register my windows product. So, built a script to do that. I wanted to know if it uses COm itnerface or web services API, or something else. How will i find it?