Near the top of the Filter Panel is the "Show Completed" checkbox. Unless this box is checked, the completed tasks will be hidden in your task list.

Below it is the Search box. If you type in your search text and then hit enter or click on the blue search icon, your task list will show all the tasks that contain that text. So you can see all tasks concerning Tom, for example, ready for an upcoming call or meeting.

If you use the red search icon, each task's notes will also be searched for the text you want.

Below the search box there is the Filter Tree, which contains many different ways in which you can filter your tasks. This is explained in the chapter entitled Searching & Filtering.

You can expand or hide the items in any of the filter categories, by clicking on the icon to the left of the filter category title.

You can also use the Filter Panel to filter which notes will be shown in the Note List.