What is a Focus, how do you use it and how does it work with Outlook Categories?

From a user: "How do 'Focuses' work and how do they interoperate with Outlook's Category field? If you have a good examples of using them, it would be very helpful. Your description of these options and "focuses" in general, made in the Getting Started guide is too short and non-informative."

Answer:

Imagine that you have a bunch of tasks, if you were to take a vertical slice thru them, you could think of each of the slices as a grouping of tasks assigned to a Project.  Taking that same set of tasks, a focus can be thought of as a horizontal slice thru the tasks.  The slice crosses project boundaries and groups according to their focus, e.g. @Phone could represent all of the tasks that require you to make a phone call, or @Errand could be all of the tasks that require you to be out and about to complete such as buying batteries or picking up a grocery list.  In David Allen's Getting Things Done book he talks about 'contexts' - our tool represent context as a 'focus'.  If you haven't already done so - I encourage you to pick up a copy of David's book - you can find a pointer to it and other interesting books at my [Recommended Reading] [1] list.

Regardless of how you assign a task to a project and/or a focus, the tool is representing (storing) that assignment in the task object's Categories field.  In this way, you can use Outlook's ability to manipulate Categories and set up custom views using your Projects and Focuses simply by using Outlook's built-in Category field.