MARGINS are a quadtuple of left, top, right, bottom. They define an inner portion of a rectangle;
the left-margin says how many pixels counted from the left border you go into the rectangle, the right-margin says how many pixels counted from the right border you go into the rectangle, etc:
Illustrates pretty ok what margins are.
Sizing margins define how an image is stretched using
nine-grid-drawing. For indepth info, see
http://msdn.microsoft.com/en-us/library/bb189722.aspx .
Content margins define where the content is placed inside a control, regardless of stretching it (since we define how many pixels to go from a border using margins).
caption margins are the same as content margins, but for title/captionbars.
none-margins is a VSB thing to display the exact borders of an image by using (0,0,0,0) as a margin structure.