It describes followers-only mode as 'Politely request other instances to only show this post to your followers' and direct mode as 'Politely request other instances to only show this post to users you mentioned'
https://mediapl.fediverse.pl/media/10/04/3b/10043bef10180e5df441468bb11ecaddb65ac66ef99209351e0a28a8b9063a9d.png