A Web service is a collection of functions that are packed together as a single entity and exposed to the network for use by other programs over the Internet. In other words, it is a Uniform Resource Locator (URL)-addressable resource that programmatically returns information to clients. Web services can be considered as building blocks for creating distributed systems over the Internet. Some examples of Web services are
A credit-checking service that returns credit information against a social security number.
A stock quote service that returns the stock price associated with a specified ticker symbol.
A purchasing service that allows purchase of supplies against an item code and quantity.