Story Types allow us to organize content in a more hierarchical way, which promotes better content discovery.
Story types are specific to each site, and shared across verticals. They are not required to publish a post.
A post’s Story Type is displayed about the headline on a permalink, and have dedicated stream pages where an optional image and description will display. They can also be added to the site navigation, just like a tag page.
Full instruction can be found in the Product team’s Story Types guide.