REST API Explained for Beginners: Endpoints, Methods, Status Codes and JSON

Your website talks to payment gateways, WhatsApp, Google Maps and SMS services through APIs. A REST API is the most common style: a set of URLs (endpoints) that accept HTTP requests and usually return JSON.

The restaurant analogy

You (the client) don't go into the kitchen (the server). You give an order to the waiter (the API) in a standard format, and the waiter brings back your food (the response).

Key concepts

• Resource: a thing, such as bookings, cars or customers
• Endpoint: the URL for a resource, e.g. /api/bookings
• Method: what you want to do
• Response: data (usually JSON) plus a status code

HTTP methods

Status codes

A tiny PHP endpoint

<?php
header('Content-Type: application/json');
$method = $_SERVER['REQUEST_METHOD'];

if ($method === 'GET') {
    $res = $conn->query("SELECT id, route, fare FROM routes ORDER BY route");
    echo json_encode($res->fetch_all(MYSQLI_ASSOC));
} elseif ($method === 'POST') {
    $data = json_decode(file_get_contents('php://input'), true);
    if (empty($data['route'])) {
        http_response_code(400);
        echo json_encode(['error' => 'route is required']);
        exit;
    }
    // insert with a prepared statement…
    http_response_code(201);
    echo json_encode(['ok' => true]);
} else {
    http_response_code(405);
    echo json_encode(['error' => 'Method not allowed']);
}

Call it from JavaScript with fetch. See fetch and AJAX tutorial.

Authentication

• API keys in headers (e.g. Authorization: Bearer <token>) for server-to-server calls
• Never put secret keys in frontend JavaScript; anyone can see them
• Use HTTPS always
• Rate-limit public endpoints

Testing APIs

Tools like Postman, Insomnia, or curl in the terminal let you send requests and inspect responses.

FAQs

What's the difference between an API and a website?

A website returns HTML for people; an API returns data (usually JSON) for programs.

What is GraphQL?

Another API style where the client asks for exactly the fields it needs. REST is simpler for most small projects.