CSS Box Model - used to create the design and layout of web pages. It is also used to create a definition for the way the HTML Elements are organized on the screen.
Four parts of a box.
Content Edge
Padding Edge
Border Edge
Margin Edge
Content Edge - this box is sized using the width and height property and applies directly to the element. This area consists of image,text, or other forms of media.
Padding Edge - this is the space immediately surrounding your element. Think of it as the air around your content.