TL;DR
event.preventDefault()
Prevents the browsers default behaviour (such as opening a link), but does not stop the event from bubbling up the DOM.event.stopPropagation()
Prevents the event from bubbling up the DOM, but does not stop the browsers default behaviour.return false;
Usually seen in jQuery code, it Prevents the browsers default behaviour, Prevents the event from bubbling up the DOM, and immediately Returns from any callback.
One should checkout this really nice & easy 4 min read with examples from where the above piece was copied from.