An API is like a magic box. We send data — in a specified format. We then get data back — in a specified format.
This magical box is simply a script kept on a server. It acts as a gatekeeper — we tell the gatekeeper that we would like to know, change, or delete something, and the gatekeeper will (hopefully) perform the action we request and let us know how it went.
Fortunately, APIs are generally very well documented and follow the same usage patterns. The vast majority of Web APIs use the representational state transfer (REST) structure — which sounds far more complicated than it is.
An interesting link found among my daily reading