Dashicons is the official icon font since WordPress admin as of 3.8.
However, it will only be available within WordPress Admin. If you would like to include and use all these free icons at the frontend liked in the Pages, Posts and others, you can copy and paste the below code into your theme functions.php:
add_action( 'wp_enqueue_scripts', 'tt_load_dashicons_frontend' ); public function tt_load_dashicons_frontend() { wp_enqueue_style( 'dashicons' ); }