overflowoverflow: visible: Non-fitting content spills outside of the edges of the box for all to see. Default.
overflow: hidden: Box is clipped, non-fitting content is unseen and the browser does not offer a way to see it.
overflow: scroll: Box is clipped, non-fitting content is initially unseen and the browser offers up a scrolling mechanism (or equivalent) so that the it can be seen upon user interaction.
overflow: auto: Browser dependent, but typically similar to scroll.