During the Iteration Planning meeting, stories and sometimes defects are broken down into tasks. The tasks are all the work the team must complete to develop, test and accept the story as done.  Tasks typically range in size from 1 hour to 2 days, depending on the length of the iteration. Two-week iterations ideally have tasks of 8 hours or less, and four week iterations have tasks sized at 2 days or less. Tasks larger than these guidelines should be broken down further to allow the team to incrementally complete the work and show progress.

The entire team works together to come up with the tasks for all the stories identified for the iteration. The majority of the tasks are determined during the iteration planning meeting, but in some cases the team may discover tasks as the work starts. It is appropriate to add and/or remove tasks on stories during the iteration.

When a task involves an external group - perhaps you want to demo your system to some project stakeholders, or deploy a testable version into your QA/test environment - then you should consider including the task as a reminder to coordinate with those groups.