Awareness
As long as a non-player entity (NPC) knows you exist nearby or can perceive you, they are Aware of you. If they can’t be sure you exist and can’t perceive you, they are Unaware of you. You may drop awareness at any time to make others unaware of your presence. Attacking or directly engaging with an unaware NPC causes them to become aware of you.
Similarly, you need to know an NPC exists nearby or be able to perceive them to be aware of them. Otherwise, you are unaware of them.