What is the "Story" under Task edit screen!?

[Andy - PTC Redundant]

When creating or editing a Task in the Sprint or Backlog, there is this drop-down menu "Story"

When clicking on it the only answer available to select is "none".

There under in small text is written "The story that is parent of this task"

It's quite clear (based on the question in the link below) that the heavily desired structure of Epic -> Story -> Task -> Sub-task is not possible in Jira, so does anyone know the purpose of this!? 

I will upload a screen shot if possible after submitting question.

https://community.atlassian.com/t5/Jira-questions/How-to-add-task-to-a-story/qaq-p/292666 

[Nic Brough -Adaptavist- · Accepted solution]

That is a custom field that one of your admins has added.  You'd need to ask them what it's for and what it should do.

[Andy - PTC Redundant]

That is super bizarre that they created. Thanks @Nic Brough -Adaptavist- for the clear answer and super fats response.

[Andy - PTC Redundant]

Herewith the screenshot: