WebServices are a way for programs to talk to each other via the Web. In essence, they're a Web-based (and thus more bloated and more trendy) reiteration or RPC.
Amazon offers a lot of information about books and ways to sell them via a SOAP interface, so you can display specific information about books available at Amazon on your own WebSite (perhaps listing all the books you authored). This information will remain in sync with the database at Amazon.
Google let you use their search engine programmatically by way of a SOAP interface.
There are many more examples.
4 pages link to WebServices:
