A Web service involves a service provider and a service requester (client). Because Web services feature language transparency, it doesn’t matter whether the underlying system that provides the service is written in Java while the client is written in Perl, Python or Ruby. For example, through Web services a Windows server can interact with a Linux server or serve an application to computer desktops, laptops or smart phones and other mobile devices over the World Wide Web.
The term "Web service" 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 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.

Web services allow different organizations or applications from multiple sources to communicate without the need to share sensitive data or IT infrastructure. All information is instead shared through a programmatic interface across a network. This interface can then be added to a GUI, like a web page, to deliver specific functionality to users. Due to this, web services are not specific to one programming language or operating system and do not require the use of browsers or HTML.
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.
The term "Web service" 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 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.
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 are used for a variety of applications, but the most common is for reusing code and connecting existing programs. The web service method can help developers segment applications into components that can be used and reused for various needs. For example, more than one program might need a conversion tool or a reporting function. This is possible due to web services’ universal communication protocols.
Web services are almost like normal a web page. The difference is that they are formatted to make it very easy for a program to pull data from the page, to the point of probably not using any HTML. They generally also are more reliable as to the consistency of the format, may use a different formal process to define the content such soap or raw xml, and there is often also a descriptor document that formally defines the structure for the data.
"All the standard Web Services works using following components:" ... the problem with this answer is that it suggests that web services do or must operate within the SOAP/WSDL mechanism. This is inaccurate. Representational State Transfer (REST) is another very popular paradigm for implementing web services. Some major websites have deprecated their SOAP services in favor of REST web services. – scottb Jul 7 '15 at 15:50 
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