A “Story” or a “User Story” in Jira terminology is a work to be done expressed (in text) as “persona + need + purpose”. In other words it is a software feature written from a perspective of an end-user. A “Story” in Jira has the following icon: 
Its purpose is to describe, how the final feature will bring a value to the customer/end-user.
The “Story” is not a “Task“. The “Story” can be split into multiple tasks later in planning process.
How to write a user story
A general “template” for writing user stories is the following:
“As a [persona], I [want to], [so that].”
For example:
- As a project manager I want to see tasks displayed in a list, so that I can quickly see the latest one.
- As a CEO I want to see the customer churn stats, so as I am able to sort through it and take appropriate action.
- As a software engineer I want to be notified about the problems in the app immediately after they happen, so as I am able to assess if this is a high-priority problem to be solved
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