API is an interface for application development
The abbreviation API stands for application programming interface. API is colloquially referred to as a programming interface.
API lets other programs have the chance to connect to the software system with its help. It’s then possible for developers to influence the hardware, such as the printer or the hard drive, without speaking directly to it. The operating system as an interface then comes into question, which receives the program via the libraries query and transfers it to the hardware.
APIs share data between programs
The term API is also used in web services. It allows developers to incorporate content into an own program through the interfaces provided. APIs are used for the exchange and processing of data and content between various websites, programs and content providers. In addition, it allows third party access to data pools and user groups which were previously sealed.
Technically speaking, APIs are something like the mechanical equivalent of the user interface which is optimised for humans and can be read by humans. The API is an interface for software and therefore solely machine readable. The API provides access to the functions of the back end. Moreover, data in a reduced form which can be easily processed further can be exchanged.
There are four different kinds of web APIs: Internal APIs, external APIs, platform APIs and authentication APIs and authorisation APIs.
You can find more information on APIs on Wikipedia: https://en.wikipedia.org/wiki/Application_programming_interface