What is an API?
A set of rules for how one program can ask another for data or actions.
Your weather app doesn't own a weather station. It asks another company's software for the forecast. That conversation happens through an API.
What it is
An API, an application programming interface, is a set of rules for how one program can ask another for data or actions. Think of it like a restaurant menu: here's what you can order, and here's how to ask.
How it works
The app sends a request to a specific address, called an endpoint, with the details it needs, like a city name. The other side checks the request, does the work, and sends back a response, usually as JSON. You never see their code. You only see the menu.
Why it matters
APIs let teams build on each other. Payments, maps, email, logins: most apps are stitched together from other people's APIs.
