Glossary

API

Definition: An Application Programming Interface is a set of rules and protocols that allows different software applications to communicate with each other.

An API (Application Programming Interface) defines how software components interact. It exposes a set of endpoints, functions or data structures that developers can call without needing to know the internal implementation. APIs are the glue that connects the modern web — they power everything from payment gateways to social logins to weather widgets.

How an API Works

  1. A client application sends a request to the API endpoint (usually over HTTP).
  2. The API server processes the request, interacts with a database or service, and prepares a response.
  3. The server sends back a response — typically JSON or XML — with the requested data or a status code.

Types of Web APIs

  • REST — Uses standard HTTP methods. Most common type today.
  • GraphQL — Query language that lets clients request exactly the data they need.
  • SOAP — XML-based protocol, common in enterprise and legacy systems.
  • WebSocket — Bidirectional real-time communication over a persistent connection.

API Keys and Authentication

Most public APIs require authentication via an API key, OAuth token or JWT to identify the caller and enforce rate limits.

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