API

Definition

An API (Application Programming Interface) is a set of defined rules and protocols that allows different software applications to communicate with each other. It acts as a contract between two systems, specifying exactly how requests should be made and what responses to expect.

Why it matters

APIs are the backbone of the modern web. They let developers build on top of existing services without needing to understand their internal workings – the same way you use a TV remote without knowing how the television processes signals. Without APIs, every app would have to build everything from scratch.

Example

When you log into a website using your Google account, that site is calling Google’s API. When a weather widget shows today’s forecast, it’s pulling data from a weather service’s API. Stripe, Twilio, and OpenAI all expose their functionality through APIs.