Finds images that have at least one of the words:
white elephant

Use "+" to find images that contain both words:
+white +elephant

Find images that contain the word "white" but rank the results higher if they have the word "elephant" too:
+white elephant

Use "-" to find images that contain "white" but not "elephant"
+white -elephant

Find images that start with "white" -- e.g. "whiter," "pair"
white*