What are the differences between a CMS and an admin system/admin area in web development?

A CMS (Content Management System) is a software application that allows users to create, manage, and modify digital content on a website without needing technical knowledge. An admin system or admin area, on the other hand, is a part of a website where administrators can manage the website's settings, users, and content. While a CMS typically includes an admin area, not all admin systems are CMSs.

// Example of a simple admin system in PHP

session_start();

if(isset($_POST['username']) && isset($_POST['password'])){
    $username = $_POST['username'];
    $password = $_POST['password'];

    if($username === 'admin' && $password === 'admin123'){
        $_SESSION['admin'] = true;
        echo 'You are now logged in as admin.';
    } else {
        echo 'Invalid username or password.';
    }
}

if(isset($_SESSION['admin'])){
    // Display admin dashboard and functionality here
} else {
    // Display login form
    echo '<form method="post">
            <input type="text" name="username" placeholder="Username">
            <input type="password" name="password" placeholder="Password">
            <button type="submit">Login</button>
          </form>';
}