Web服务是一种服务导向架构的技术，通过标准的Web协议提供服务，目的是保证不同平台的应用服务可以互操作。

根据W3C的定义，Web服务（Web service）应当是一个软件系统，用以支持网络间不同机器的互动操作。网络服务通常是许多应用进程接口（API）所组成的，它们透过网络，例如国际互联网（Internet）的远程服务器端，执行客户所提交服务的请求。

尽管W3C的定义涵盖诸多相异且无法介分的系统，不过通常我们指有关于主从式架构（Client-server）之间根据SOAP协议进行传递XML格式消息。无论定义还是实现，WEB服务过程中会由伺服机提供一个机器可读的描述（通常基于WSDL）以辨识伺服机所提供的WEB服务。另外，虽然WSDL不是SOAP服务端点的必要条件，但目前基于Java的主流WEB服务开发框架往往需要WSDL实现客户端的源代码生成。一些工业标准化组织，比如WS-I，就在WEB服务定义中强制包含SOAP和WSDL。

A Web service is a service offered by an electronic device to another electronic device, communicating with each other via the World Wide Web. In a Web service, Web technology such as the HTTP, originally designed for human-to-machine communication, is utilized for machine-to-machine communication, more specifically for transferring machine readable file formats such as XML and JSON. In practice, the Web service typically provides an object-oriented Web-based interface to a database server, utilized for example by another Web server, or by a mobile application, that provides a user interface to the end user. Another common application offered to the end user may be a mashup, where a Web server consumes several Web services at different machines, and compiles the content into one user interface.