The box model is a box that wraps the HTML element. According to the box model concept, element of every is a rectangular box and may have width, height, padding, borders, and margins. There are few new properties in CSS, to better understand.
The perimeter of each of the four areas (content, padding, border, and margin) is called an "edge", so each box has four edges:
content edge or inner edge
The content edge box in the rectangle given by the width and height of the box, which often depend on the element's rendered content. The four content edges define the box's content box.
The padding edge surrounds the box padding. If the padding has 0 width, the padding edge is the same as the content edge. The four padding edges define the box's padding box.
The border edge surrounds the box's border. If the border has 0 width, the border edge is the same as the padding edge. The four border edges define the box's border box.
margin edge or outer edge
The margin edge surrounds the box margin. If the margin has 0 width, the margin edge is the same as the border edge. The four margin edges define the box's margin box.