This hook is theme-dependent which means that it is up to the author of each WordPress theme to include it. It may not be available on all themes, so you should take this into account when using it. However, it is included in the default Meta widget when that widget is in use.

This hook is an action which means that it primarily acts as an event trigger, instead of a content filter. This is a semantic difference, but it will help you to remember what this hook does if you use it like this:

function your_function() {
	echo '<li>This text is inserted into the sidebar.</li>';
}
add_action('wp_meta', 'your_function');
?>