Facebook Stories launched globally in March, you could only share to all their friends or a subset of them. Now if you allow public followers, you can post your Story publicly so anyone can watch.
Facebook Story public, first tap on the Add To Story button on the home screen, and post a photo or video. Then view your own Story and tap the three dots ‘more’ button in the top right. Open “Edit Story Settings” and change from “Friends” to “Public”. All your existing Facebook Stories from the last 24 hours plus any you share from then on will be publicly visible to anyone. You can tap on the viewer count to see the names of friends who’ve viewed your Story, and a count of all the additional followers who saw it without their names.