The term Web services describes a standardized way of
integrating Web-based applications using the XML, SOAP, WSDL
and UDDI open standards over an Internet protocol backbone.
XML is used to tag the data, SOAP is used to transfer the
data, WSDL is used for describing the services available and
UDDI is used for listing what services are available. Used
primarily as a means for businesses to communicate with each
other and with clients, Web services allow organizations to
communicate data without intimate knowledge of each other's
IT systems behind the firewall.

Unlike traditional client/server models, such as a Web
server/Web page system, Web services do not provide the user
with a GUI. Web services instead share business logic, data
and processes through a programmatic interface across a
network. The applications interface, not the users.
Developers can then add the Web service to a GUI (such as a
Web page or an executable program) to offer specific
functionality to users.

Web services allow different applications from different
sources to communicate with each other without
time-consuming custom coding, and because all communication
is in XML, Web services are not tied to any one operating
system or programming language. For example, Java can talk
with Perl, Windows applications can talk with UNIX applications.

Web services do not require the use of browsers or HTML.

Web services are sometimes called application services.