Task

Task is a unit of work. When stories are broken down to each unit of work then it is called task. These tasks can be split between multiple developers. Whether it is a small story or large one splitting into tasks gives clear idea on pieces of development.

Just from experince in one of my projects, I have seen when we divided a user story into 5 tasks and updated board then one of the developer recognized that one of the task is very similar to what he is planning to do in his user story. Sounds helpful? Communication is critical part for any project and having a user story into tasks provides clear visibility to whole team of what we are up to and what path we are taking to complete this user story.

Also sometimes a user story can be can be planned into tasks considering specialty of team members.Like, developer X is too good and fast in UI design and having a task just for UI screen make sense and developer X can take it. Well I am just saying it to express that we have that flexibility, it doesn't mean that we should not give opportunity to other interested developers to take up UI work.