Backend widgets are boxes of content that are displayed in the backend dashboard. Widgets are plug 'n play, meaning that if you upload a widget folder it is automatically loaded. A widget is defined by a folder named .widget in the end e.g. admin/mywidget.widget/. Inside the folder you need to create a configuration file config.inc.php that defines the widget and the file to load. See below for an example.

admin/mywidget.widget/config.inc.php

  return [
    'name' => 'My App',
    'file' => 'widget.inc.php', // The file to load that is holding the content
    'priority' => 0,
  ];

admin/myapp.widget/widget.inc.php

  <h1>Hello World</h1>
  <p>Lorem ipsum dolor</p>

• How to Create An Admin App