why do we use margin in css code example

Example: margin css

/* Apply to all four sides */
margin: 1em;
margin: -3px;

/* vertical | horizontal */
margin: 5% auto;

/* top | horizontal | bottom */
margin: 1em auto 2em; 

/* top | right | bottom | left */
margin: 2px 1em 0 auto;

/* Global values */
margin: inherit;
margin: initial;
margin: unset;