APIs Services are regulated requests from one operation that have been described for the program being called upon. Such API can authorize direct and quick connection between two systems that are not communicated directly with each other. API acts as a link for information flow from application to another.
To create client application or website rich in functionality and quality, it has to be integrated with other systems through APIs. A classic example of this would be integration payment API with website for smooth payment or transaction processing.
API development allows client application to be straightly requested by other application for information. This is exclusively ideal when application is a part of business network where data wants to flow in a smoothly within company premises. Also, Service API helps client application to be adept to get bundled with mashup developments. The capability of a mashup to be served as a service makes an opportunity for client application monetization.