How does the Show filter refine my activity list?

The Show filter displays activities based on certain criteria. Here's a list of the show filter criteria for activities:

Show Filter	Tasks	Appointments
Open	All open tasks with a due date in the defined date range, and open tasks with no due date	All appointments that have a start date of today or in the future within a defined date range
All	Open tasks with no due date or with a due date within the defined date range. Closed tasks with an end date in the defined date range	Open tasks with no due date or with a due date within the defined date range. Closed tasks with an end date in the defined date range
Completed	Tasks that are completed within the defined date range	Appointments in the past with a start date that falls within the defined date range