Finds images that have at least one of the words:
hot dog

Use "+" to find images that contain both words:
+hot +dog

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

Use "-" to find images that contain "hot" but not "dog"
+hot -dog

Find images that start with "hot" -- e.g. "hotter," "hottest"
hot*