An API is a connection between computers or between computer programs
An application programming interface or API is a connection between computer programs. The term API is an acronym, and it stands for “Application Programming Interface.
API is a software interface or contract which offers a service to other parts of software. APIs usually come with a documnetation which describes how an API can be used, this document is called API specification.
APIs let services communicate with other services and apps without having to know how they are implemented in detail. This can help you simplify the app development. When you are developing apps or redesigning existing platforms, APIs give you flexibility and help you simplify the design and provide better user experience.
APIs can be implemented using different standards, some of established standards are: