What is a web service? The W3C describes a Web Service as "a software system designed to support interoperable machine-to-machine interaction over a network". This means that a connection can be established between two computers regardless of operating system or programming language. As long as both sides recognize the protocol used, they can communicate. In short, a web service allows you to connect to it and perform queries on the data and functions that it holds just as if you were using the service on your own server. The service could be anything from a post code validation service to a blog that allows you to edit the contents from elsewhere.