By default, the title of the Poster Item defines the automatically generated permalink.
This link can be shared and will also be used by the Social Share Buttons Stack. It is possible to override this permalink generation by a self defines slug.
Please make sure that either the title or the slug are unique all over the blog. If these are not unique, you will see duplicated content when navigating to the detail view.
An example for a permalinked post is https://support.instacks.com/poster-stack-2/?post=permalink, where permalink is the generated part from the title or slug.