The software world
API
Application Programming Interface
How one program asks another to do something — a defined set of requests a service agrees to answer. When an app shows you the weather, it's quietly asking a weather service through its API. It's a menu of what you're allowed to order, and the format for ordering.
Why it matters
Part of Software words you'll hear → "Use the X API" just means "have your code talk to X's service in the way X documented."