Planning Poker - reference story? Is it Functional Story or Development story?

Should it be Functional story or the Development story?

What is a Functional Story? What is a Development Story?

Whatever it is, why is it in a backlog if it is already done?

@Ian, sorry for the confusion. Done stories are not in the backlog.

Here I would like to understand what is the best Story to pick up at the time of Planning Poker?

Don’t they all have to be estimated? Why would any one be better than another for estimation purposes, including as a point of reference?

Has the attempt to distinguish between so-called “functional stories” and “development stories” introduced unnecessary complication?

@Ian, Thank you for the response.

So what is the best REFERENCE STORY in Planning Poker? Is it a Story which is already Done or a Story from the Product Backlog?

Yes, I agree that "Functional Story" and "Development Story" created complication here, but I came across this question recently in the project.

How to deal with this?

So what is the best REFERENCE STORY in Planning Poker? Is it a Story which is already Done or a Story from the Product Backlog?

Which do you think would provide the best evidence to the team about the amount of work involved, so as to anchor their understanding?

It would be the Story which is already Done, as team has already worked on it and have the visibility.

Coming back to my old question, "Functional Story" and "Development Story". Have you came across these terms?

No. My guess would be that the terms obliquely reference functional and non-functional requirements in some way.

Thank you Ian for assisting me with my back & forth queries.

"Functional Story" and "Development Story". 

I heard one of my acquaintances talking about these.  After further discussion I came to understand them as :

• Functional Story = stories related to new or updated product features
• Development Story = technical debt or new infrastructure needed in order to implement functional stories.

Regardless, they should all be treated equally when ordered in the Product Backlog and estimated by the Development Team.

As for your reference story question, I think the best reference story for the first time doing Planning Poker is the story in the Product Backlog that the Development Team feels they understand the best. That allows them a level of confidence in their first estimate.  The first Retrospective after the initial session will include discussion on how they felt they did in their estimation but do not go back and re-estimate. Those stories are now part of history and you don't change history. After the first round, the reference story should be forgotten and any Planning Poker sessions going forward should be done based on what was learned from preceding sessions.  Their estimates will evolve over time and become more cohesive as a group.