Basic narrative structure at the heart of behavior driven development (taken
from wiki page(https://en.wikipedia.org/wiki/Behavior_driven_development?useskin=vector).

Title
    An explicit title.

Narrative
    A short introductory section with the following structure:

        As a: the person or role who will benefit from the feature;
        I want: the feature;
        so that: the benefit or value of the feature.

Acceptance criteria
    A description of each specific scenario of the narrative with the following structure:

        Given: the initial context at the beginning of the scenario, in one or more clauses;
        When: the event that triggers the scenario;
        Then: the expected outcome, in one or more clauses.

Example:

Title: Returns and exchanges go to inventory.

As a store owner,
I want to add items back to inventory when they are returned or exchanged,
so that I can track inventory.

Scenario 1: Items returned for refund should be added to inventory.
Given that a customer previously bought a black sweater from me
and I have three black sweaters in inventory,
when they return the black sweater for a refund,
then I should have four black sweaters in inventory.

Scenario 2: Exchanged items should be returned to inventory.
Given that a customer previously bought a blue garment from me
and I have two blue garments in inventory
and three black garments in inventory,
when they exchange the blue garment for a black garment,
then I should have three blue garments in inventory
and two black garments in inventory.