I believe it's for how quick or fast a players react to offensive or defensive situations, in gameplay.
For example, a player like Big Ben who has a terribly high defensive rating woll automatically run down the court to defend once the opposing team grabs possession. The same goes for players with high offensive ratings, lke Iverson.
Once their team gets the ball, even if it's just a teammate's rebound, you can expect that player to immediately be running down the court on offense.
I find this very useful, say, in guarding the passing lanes, as with inbound plays. Players like Big Ben or Ron-ron will react faster, therefore leading to a higher possibility of stealing the ball. This is opposed to players with low def awareness, like Brent Barry or Palacio in the game who will rarely or not quickly be watching the ball nor the ball handler to enable them to react quickly on defense, be it stealing or switching to open shooters. It's like the high def rating makes players more aware of when to defend, and they are ready to 'face' the enemy earlier.
Same goes for the offense. Players with high off ratings are the ones who usually get the bulk of my fastbreak points, as they are the ones who are 'eager' to score and are always the first to react to a scoring opportunity for my team.
Gordon # 7, Primacy is for simulations or CPU controlled teams. This rating helps the computer determine which player to give the ball to more often on possessions, which translates into more points for that player on the stat sheet after games. Player who are their team's number one options, like Kobe, or Paul Pierce, have a high rating for this stat.
Hope I helped.
