API

An Application Programming Interface (API) is a contract that lets one program talk to another without needing to know its internals — your frontend asks an API for data, the API processes the request and returns a response. Most web APIs today are accessed over HTTP and exchange data as JSON.

• —Almost every app you build will call at least one API — your own backend, or a third party.
• —A well-designed API is predictable: consistent URLs, clear responses, sensible error messages.
• —Understanding APIs is the bridge between frontend and backend, and between your app and the outside world.

This is the exact lesson that covers this term in depth — with examples, diagrams, and a hands-on exercise.