Margin is the space outside the border and outline displays the outside edge of the margin when the block has the browser's focus.
Border is the frame between padding and margin.
Padding is the space between the content and the border and background colors display behind background images which display behind content.
Content items such as images and text include Line-height which is the height of one line of content (see highlight below).
Lorum ipsem unim a yada mattata. usto lorem eget velit libero elit amet, ac in lorem dui feugiat lectus cursus. Placerat porta tempor morbi leo libero, sit odio in scelerisque eu nonummy tellus, neque quam semper posuere ante consectetuer id. Congue donec volutpat integer a tempus, etiam nulla vestibulum.