Especially handy when you've thrown the hero out the door with a problem, no way to get back, and no knowlege of what he can do next to solve it. Let him walk into a village where a tree is covered with bejeweled fruit, or go through a door to find himself passing from a train station to a mountain top with gargoyles, or see a house being lit on fire by a dragon. It gives him something to do. In due course, someone he meets along the way can give him some knowledge of his possible solution.
But what if the story doesn't allow random wonders? If a less magical world is necessary for the plot, either to avoid distracting from the central issue or to keep the hero from solving it too readily?
Then things get ugly while trying to wrench some interesting notion of what might happen next from the muse while not throwing in anything that would obviously have to be jettisoned later.