Web services, as the term says, provide a service. It might be a price check, an inventory status check, a stock quote, or an airline reservation. Examples of web services include:
Intelligent product catalog searches
Product availability checks
Pricing inquiries
Customer credit checks
Order status checks
Vendor-managed inventories
Demand forecasts, stock replenishment
Dynamic auctioning and bidding
Publishing and analyzing financial reports
Electronic bill presentment and payment
Matching vacancies and job applicants' profiles
Postal service address checks
Universal Description, Discovery, and Integration (UDDI) registration and discovery