Quite simply, one's awareness of one's physical surroundings and current situation. Situational awareness, or SA, is of great use in many sports and games, but is most highly valued in real life situations like warfare and driving. Air force pilots tend to stay alive longer if they are more aware of the positions and velocities of all other aircraft in their immediate vicinity. The same goes for civilian drivers and other cars, peds, road signs, obstacles, etc. More specifically, how far do you drive in front of yourself? On the highway, are you aware of what the traffic's doing a mile in front of you? How about the people up to a half a mile behind you? If you are, count yourself lucky - you're paying more attention that probably 90% of the other people on the road.