# What a Web Service is ?

This tutorial explains to you what is a web service.

Web services drive communication on the web, and they have been at the core of modern application architectures for many years.

A web service is a function that can be accessed by other programs over the web (HTTP). The term "web service" describes a standardized way of integrating applications (generally web-based, but not only) using the XML, SOAP, WSDL and UDDI open standards over an Internet protocol backbone. XML is the data format used to contain the data and provide metadata around it, SOAP is used to transfer the data, WSDL is used for describing the services available and UDDI lists what services are available. A web service is a method of communication between two electronic devices over a network.

This can be seen in the following picture:

If we want a definition from www.w3.org here it is one: A Web service is a software system designed to support interoperable machine-to-machine interaction over a network. It has an interface described in a machine-processable format (specifically WSDL). Other systems interact with the Web service in a manner prescribed by its description using SOAP messages, typically conveyed using HTTP with an XML serialization in conjunction with other Web-related standards.

The request and response are platform/ software independent, so a .NET application can talk with a Java or Ruby application for instance.