Each of these regions have their own special properties:
North - Anything in this region will always be at the top of the container. An excellent example of this is a Toolbar.
Anything in this region will expand horizontally, but not vertically.
East - Anything in this region will always be at the right of the container. Always above a "South" container, and below a "North" container.
Anything in this region will expand vertically, but not horizontally.
South - Anything in this region will always be at the bottom of the container. An excellent example of this is a Status bar.
Anything in this region will expand horizontally, but not vertically.
West - Anything in this region will always be at the left of the container. Always above a "South" container, and below a "North" container.
Anything in this region will expand vertically, but not horizontally.
Center - Any component placed in this region will expand both vertically and horizontally. This region would normally be used for placing a component which would benefit from window growth, e.g. a TextArea for a TextEditor, or an Image for a picture viewer.