yii2-app-basic/views/site/about.php

<?php
use yii\helpers\Html;

/**
 * @var yii\base\View $this
 */
$this->title = 'About';
$this->params['breadcrumbs'][] = $this->title;
?>
<div class="site-about">
	<h1><?php echo Html::encode($this->title); ?></h1>

	<p>
		This is the About page. You may modify the following file to customize its content:
	</p>

	<code><?php echo __FILE__; ?></code>
</div>