Let’s have a discussion about what the API is
API, an abbreviation of application program interface, is a set of routines, protocols, and tools for building software applications. A good API makes it easier to develop a program by providing all the building blocks. A programmer then puts the blocks together.
API is a protocol intended to be used as an interface by software components to communicate with each other. An API may include specifications for routines, data structures, object classes, and variables. An API specification can take many forms, including an International Standard such as POSIX, vendor documentation such as the Microsoft Windows API, the libraries of a programming language, e.g. Standard Template Library in C++ or Java API.
API libraries and frameworks
An API is usually related to a software library: the API describes and prescribes the expected behavior while the library is an actual implementation of this set of rules. A single API can have multiple implementations (or none, being abstract) in the form of different libraries that share the same programming interface.
An API can also be related to a software framework: a framework can be based on several libraries implementing several APIs, but unlike the normal use of an API, the access to the behavior built into the framework is mediated by extending its content with new classes plugged into the framework itself. Moreover the overall program flow of control can be out of the control of the caller, and in the hands of the framework via inversion of control or a similar mechanisms.
Google has proved lot of API by which we can make our work easy. Its mostly appreciable by all the application programmers.