An individual unit of work in Jira is referred to as an issue. This issue could be a unit such as a STORY or an epic. EVERY issue has a field called issue type, which represents the type and use of the issue. For instance, in a Scrum project, one would have the following types of issues by default:

• Story: A story in Jira represents a SINGLE feature that is to be implemented. It is generally used in order to get the requirements from the end user's PERSPECTIVE. For this purpose, stories are often written in non-technical language. These are used for focusing on the end results of the feature.
• Epic: An epic means a big user story. This represents that the story has not been broken down into smaller and FINER requirements. In Jira, epics are mostly used to define the "theme" for various stories that will be part of it, along with the modules or the major components in a big development project.
• Bug: A bug in Jira represents a problem or a defect that needs to be fixed in a given product.
• Task: This represents a generic task that is neither a bug nor a story, but it needs to be completed.