What is an API?
TL;DR: An API (Application Programming Interface) is a set of rules that allows different software applications to communicate. When you check weather on your phone, the app uses an API to request data from a weather service — the API defines how to ask and what format the answer comes in.
APIs come in several styles: REST (most common web APIs), GraphQL (flexible queries), WebSocket (real-time), and gRPC (high-performance). REST APIs use standard HTTP methods (GET, POST, PUT, DELETE) and typically return JSON data.