The area where your content is displayed, which can be sized using properties like width and height.
The padding sits around the content as white space; its size can be controlled using padding and related properties.
The border box wraps the content and any padding. Its size and style can be controlled using border and related
The margin is the outermost layer, wrapping the content, padding and border as whitespace between this box and other elements. Its size can be controlled using margin and related properties.