Newbie - Web Service Examples

[slinky]

Thanks in advance.... I need to get a better picture of the use
of .net Web Services.

Some questions too:

What would be the advantages of a Web Service as opposed to a web-site
app? (my first thought is that the web service would move data more
efficiently due to having a genuine "client app" on the user end -
correct me if wrong).

Are there any online examples of the use of web services? I'm trying
to get a feel for how would a business need be determined better for a
Web App or a Web Services App....

Thanks!