This isn’t the first time researchers have been able to make a liquid float. It’s actually been done several times before, using other techniques to make liquids levitate.
Usually, a denser (more dense) substance will sink below a less dense substance. (For example, when water boils, air bubbles rise to the surface of the water, because they are less dense.)
So, normally, the liquid that the researchers used would fall, because it is denser than the air around it. But when the container holding the liquid is shaken rapidly, the liquid acts unnaturally – it defies gravity and stays afloat. The container vibrating actually compresses the air below the liquid, which prevents it from falling down.