Precondition Epics are larger Stories. In the Storymap Tree you can have as many levels of Epics as you like to describe the project. Once you reach a level which cannot be broken down into smaller parts, you create Stories.
The state of the Precondition Epic will always mirror the state of the Stories/Epics below it.
See more details on Epics and Stories and how they are represented in Agemba here.
Below is an illustration of an ordinary Story, highlighting common icons displayed on cards and what they represent: