So web serivces is basically == RPC (Remote Procedure Call) == RMI (similar if only using Java)
Web services is a way of doing remote Method Invocation
Then Web Services is == Java RMI + ability to invoke methods on other languages / platforms (e.g. .NET / Perl / PHP ..etc)
besides RPC / remote Method Invocation, what web services can do Or that's it for web serivce which is RPC.

Web Service RMI
hawklixingyi
This article is an excellent explaination of what web services are and are not
http://weblogs.cs.cornell.edu/AllThingsDistributed/archives/000343.html
SteveGY_CN
Hello,
Web services can be used in a RPC/RMI fashion, but they are actually a much more general purpose messaging mechanism. For example, you can use web services for other message exchange patterns like one-way messaging, solicit/response, publish/subscribe. Not all web service platforms support all of these message exchange patterns, but you should see much more general support in the Windows Communication Foundation.
Daniel Roth