These are the roles in Scrum. No management? That’s right
The Scrum Master may look like a traditional project manager role. Well, it is not. The role of a Scrum Master is to remove impediments and obstacles that slow the Team down from completing their work. Not enough memory or people not replying to your requests? Go to the Scrum Master.
Who does the planning then? Well, it depends. For longer time planning, the Product Owner gathers the requirements to an artifact called backlog. The backlog is a prioritized list of tasks that needs to be done. The task on top of the backlog has the highest priority. It is the responsibility of the Product Owner to keep the backlog prioritized at all times. The Product Owner also answers questions from the Team if the task is unclear.
In the Sprint backlog, which is a task list for the current sprint, it is the Team that decides what, when and in which order will be done. Since the Team will do the work, it knows best how to accomplish the work with the highest priority. It is the responsibility of the Team to transfer the tasks from the top of the backlog to the sprint. That way, the Team is committing to accomplish what is in the sprint backlog.
So where are the managers? Managers and other stakeholders talk to the Scrum Master if they have requirements about how to do the work or the Product Owner about what to do. The Team is doing the work.