API (Application Programming Interface) — a way for programs to communicate. Core part of modern development. MDN API — full explanation.
Simple example
Ordering food at a restaurant: You (Client) — request. Waiter (API) — intermediary. Chef (Server) — executor. API — the link.
REST API
Most common. HTTP methods: GET — fetch data. POST — create. PUT — update. DELETE — delete. Used with fetch() or axios.
Where is API used?
Weather apps. Social login. Payment systems. Map services. Every web app uses API.
Conclusion
API — core part of modern development. Every developer needs to understand it.
Source: MDN API, REST API Tutorial
