I'm not an expert in this by any means. But here is what I know about web services so far:
SOAP:[/] Simple Object Access Protocol allows for the transfer of files in XML across the HTTP (web) protocols in a standard format.
[b]Web Service[\b] A small application available over the HTTP protocol which can run behind the scenes.
Think of an applet or EJB that can run remotely without human intervention - an applet resides on your server and needs fixed parameters. A "web service" would reside who knows where, and you would call that service from your app, send the necessary parameters and get a response which you would use on your web page.
[b]WSDLWeb Service Description Language - a description of the service and where to find it. things like parameters, etc.
UDDI A repository for descriptions of web services. Almost like a private search engine devoted to these applications.
To learn more, check out www.silverstream.com and IBM's site regarding websphere.
It's complicated, but it's beginning to make sense to me - slowly.