why adds ‘»’ symbol?

on last WordPress when I wrote <?php wp_title(); ?> appear » symbol before the name of the page..

On my functions.php I wrote add_theme_support( 'title-tag' );

Thanks

The wp_title function is meant to be used in things like breadcrumbs where you would want something like My Blog » My Category » My Post. As such the function allows you to prepend something to your title. By default it prepends ». If you just want the title of your post or page use the_title.