WordPress at a glance
action is not described

plugin_loaded action-hook . WP 5.1.0

Fires once a single activated plugin has loaded.

Usage

add_action( 'plugin_loaded', 'action_function_name_9688' );
function action_function_name_9688( $plugin ){
	// action...
}
$plugin(string)
Full path to the plugin's main file.

Where the hook is called

In file: /wp-settings.php
plugin_loaded
wp-settings.php 351
do_action( 'plugin_loaded', $plugin );

Where the hook is used (in WP core)

Does not used.