An issue represents an action that has to be done. That action can be a task, a bug, a feature request or any type of action your organization might need to work with. Issues are the core of the Jira applications since all the team collaboration happens around the work items and their organization.You can customize your own issue types creating issue sets associated per projects, and even per permission types.
To configure the layout of the new Jira issue view—which fields appear and the order they appear in—open an issue and choose Configure at the bottom-right. To find out more about configuring the issue layout, check out Configure field layout in the issue view.