The Awareness skill reflects your ability to perceive hidden dangers and to notice small details about your physical surroundings. You use the Awareness skill to norice ambushes. spot traps and discern other threats to you and your allies. Awareness is not tied 10 any one sense; it encompasses them all.
When using Awareness to detect a hidden enemy, the Test is always Opposed. Otherwise, the thing you are trying to detect applies a Difficulty based on how cunningly concealed it is. An Awareness Test is usually a Free i made in reaction to something.