What does the Planned view show?

Planned shows only the open to-dos that have a due date. If a to-do has no date, it won't appear here. Like All, its top box is a search filter. You can switch between grouping by the list each item comes from or by the task's date (Overdue, Today, Tomorrow and so on) — the sort icon at the top right of the Planned view flips between the two.