API stands for Application Programming Interface, which is a software interface for interaction between different systems. Simply put, an API is a set of clear rules that allow one program to communicate with another, send a request, and receive a response. End users usually do not see APIs and rarely think about their existence, yet they use them constantly. Logging in with Google, paying by card on a website, displaying the weather, exchange rates, or delivery status — all of this works thanks to APIs.