API

An API (Application Programming Interface) is a set of features and rules that exist inside a software program (the application) enabling interaction with it through software – as opposed to a human user interface. The API can be seen as a simple contract (the interface) between the application offering it and other items, such as third-party software or hardware.

In Web development, an API is generally a set of code features (e.g., methods, properties, events, and URLs) that a developer can use in their apps for interacting with components of a user’s web browser, other software/hardware on the user’s computer, or third-party websites and services.