New Plan Mode
Plan mode allows users to plan issues into Components, Releases and Sprints.
In order to allow these classifications make sure that Components, FixVersion/s and Sprints fields are enabled in Manage Fields.
If there are issues with any of these fields populated they will be displayed in the board.
In order to move issues back from the Planner board click on the X at the right end of the issue (shows up when the cursor hovers over the issue).