Which JIRA issue type is often used to represent a small, well-defined piece of work within a larger project?

The "Sub-task" issue type in JIRA is typically used to represent a small, well-defined piece of work within a larger project. Sub-tasks are often used to break down larger tasks or user stories into more manageable sub-components, allowing for better tracking and management of work. They are commonly used to divide work among team members or to represent tasks that are required to complete a larger user story or task.