margin adds space outside an element. margin: 0 auto centres a block element horizontally. Vertical margins between adjacent elements collapse to the larger value. padding adds space inside the element's border.
Margin and Padding
/* Shorthand: top right bottom left */
margin: 10px 20px 10px 20px;
padding: 10px 20px; /* top/bottom | left/right */
margin: 10px; /* all sides */
margin-top: 16px;
margin-right: auto; /* auto centers block elements */
margin-left: auto;
/* Remove browser defaults */
margin: 0;
padding: 0;