This is another core concept in Permaculture. A sector is a path of energy into or out of your Permaculture System. I mean energy in its true sense (not a quasi-spiritual one). There are many potential energies that can enter and leave your land. Let's look at a few of them:
Diagram of how the sun moves in each season.
Consider the path of the Summer Sun and Winter Sun. The further from the equator you are, the bigger the difference in path, angle, duration, and intensity. Is your home facing the early morning sun? Does your garden get the western setting sun?
Diagram of sea breezes.
Do you live in an area that has Summer Winds? Do you have Winter Winds that come from a different direction? How about a salty sea breeze? Do you have seasonal storms? Does the wind always/usually blow from east to west or from south to north?
A home on the water provides unique energy flows.
Do you live on a river, lake, or other body of water? Do you have a stream or pond on your land? From which direction does the rain come?
Fire energy is an important component of planning.
Do you live in an area that has seasonal fires? Forest fires? If so, from which direction would they most likely come?
Deer dining on a square foot garden.
Where do vehicles enter and leave your property? Do you have trails accessing your land? Where does wildlife come and go? Where would a burglar try to enter and leave your property? These are paths that can carry energy on and off your land.
Not quite an "energy", but still important. If you are always concerned about the neighbors watching you when you are working in your garden or that they can see you while you are standing in your kitchen, then this is psychologically draining. If every time you walk out your back door, you can see the local shopping center over your low bushes, this ruins a bit of your mood - frankly, to me it would be depressing. On the other hand, if you walk out your front door and see mountains or a beach or a sunrise over a meadow, that can be a huge benefit. Don't discount how much a view (positive or negative) impacts your mood and how some privacy can create a stronger sense of peace.
Designing with Sectors
Viewing sectors on a map can be a bit confusing at first. Just remember that the home is the center of the circle, and all the other sectors radiate out from it. For example, using the Sector Map below, from the 10:00 position to the 2:00 position is an "Undesirable View..." (this is also from WNW to ENE if compass readings are your thing). Some sectors overlap, for instance the direction of the Winter Sun and Summer Sun.
The map below also shows the Permaculture Zones overlaid in shades of yellow and orange.
Sector Design is a vital part of planning your Permaculture System. Every place is unique, so take some time to consider how energy enters and leaves your location.