The entire team attends the Sprint Planning meeting. Working from the ordered Product Backlog, The Product Owner and the Development Team members discuss each item and come to a shared understanding of that item and what is required to complete it consistent with the current Definition of Done.
In Scrum, the Sprint Planning meeting is described as having two parts.
Choose Goal: the Team and the Product Owner collaborate to decide how much of the prioritized backlog can be turned into potentially shippable functionality.
Create Sprint Backlog: the Team defines the tasks required to build that functionality during the next Sprint, including estimates to achieve the Definition of Done.
Part One: What work will be done?
In the first part of the meeting, the Product Owner presents ordered Product Backlog Items to the Development Team, and the whole Scrum Team collaborates to understand the work.
The number of Product Backlog Items to undertake in the Sprint is solely up to the Development Team. To decide how many items to undertake, the Development Team considers the current state of the Product Increment, the past performance of the team, the team’s current capacity, and the ordered Product Backlog. The Development Team alone decides how much work to take on.
Often, but not always, the Sprint is given a goal called the Sprint Goal. This is a very strong practice which helps everyone focus more on the essence of what needs to be done, and less on small details which may not be important to what we really need to accomplish.
Part Two: How will the work be accomplished?
In the second part of the meeting, the Development Team collaborates to decide how to produce the next Product Increment in accord with the current Definition of Done. They do sufficient design and planning to be confident of completing the work during the Sprint. Work to be done in the early days is broken down into small units of one day or less. Work to be done later may be left in larger units to be decomposed later.
Deciding how to do the work is the responsibility of the Development Team, just as deciding what to do is the responsibility of the Product Owner. The Product Owner may remain during this part of the meeting, to answer questions and resolve misunderstandings. In any case he needs to be readily available.
Result of Sprint Planning
Sprint Planning concludes with the Scrum Team coming to a common understanding of the quantity and complexity of what is to be accomplished during the Sprint, and within a rational range of circumstances, expect to complete it. The Development Team forecasts the amount of work they will complete and commit to each other to accomplish it.
All Scrum meetings are time-boxed. The recommended time for Sprint Planning meeting is two hour or less per week of Sprint duration. Because the meeting is time-boxed, the success of the Sprint Planning meeting is highly dependent upon the quality of the Product Backlog going in. This is why Product Backlog Refinement is an important Scrum activity.