An application programming interface (API) is a particular set of rules or Code and specifications that software programs can follow to communicate with each other. In a simple manner it is a way when user interface facilitates interaction between humans and computers.
Type of API’s
These APIs are used exclusively within an organisation or company, SOAP/HTTP or .NET still has a large presence
These APIs are primarily available externally to consumers, the growing trend for external APIs are written based on REST/JSON technologies
These APIs are specifically designed for partners to be able to access business functions in relation to the business relationship of the partnership
Usage of API’s
By using APIs it is possible for big services like Google Maps or Facebook login twitter tweets and other application services.