Web service is an application programming interface (API) or Web API that is accessed via Hypertext Transfer Protocol (HTTP) and executed on a remote system hosting the requested service. Web services platform elements are XML, SOAP, WSDL and UDDI. XML (Extensible Markup Language) is used to tag the data, SOAP (Simple Object Access Protocol) is used to transfer the data, WSDL (Web Service Definition Language) is used for describing the services available and UDDI (Universal Description Discovery and Integration) is used for listing what services are available. It is a set of technologies that provide platform-independent protocols and standards used for exchanging data between applications. Web services are application components, communicate using open protocols, self-contained and self-describing, discovered using UDDI and can be used by other applications. API stands for Application Programming Interface. It is an interface implemented by a software program which enables it to interact with other software. API is a set of programming instructions and standards for accessing a Web-based software application or Web tool. A software company releases its API to the public so that other software developers can design products that are powered by its service. An API is implemented by applications, libraries, and operating systems to determine their vocabularies and calling conventions, and is used to access their services. APIs in Java typically consist of a set of objects that developers will use to add some functionality to a project. Many complicated tasks can be abstracted and easily performed using an API that other developers have made available. An API is a software-to-software interface, not a user interface. With APIs, applications talk to each other without any user knowledge or intervention. Solver Circle Ltd integrated and created Web APIs for many popular websites. Solver Circle Ltd’s APIs are very comprehensive and support almost all major web scripting options including flash, Ajax etc.