As with many CSS properties, you can use
margin with one, two, three or four parameters.
One param = all four sides.
Two params = vertical | horizontal
Three params: top | horizontal | bottom
Four params: top | right | bottom | left
See
https://developer.mozilla.org/en-US/docs/Web/CSS/margin.
EDIT: Darn, @theducks was faster!
P.S.: Don’t expect every reader to honor margins on every block element. Some are notorious in ignoring whatever you give them, mostly on horizontal margins.