The NEHTA approach to connectivity is based on a technology known as 'Web services'.  A Web service is simply a self-contained unit of software which:
•    provides a specific function defined by its interface (eg look-up patient details, accept a referral); and
•    is accessible on a network, using the protocols of the internet.

It is a software technology designed to support application-to-application interoperability, typically on different machines, connected by a network.