I apologize in advance for the hand waving vagueness, but here's how I think of it.
N=abstract thinker, likes ideas and concepts and big picture
S=concrete thinker, likes real things and details
J=likes rules and systems and binary partitions
P=thinks in terms of guidelines and heuristics and rules of thumb and grey areas.
Most programmers are Ns, but I have met quite a few DBAs who are Ss.
I'm a P (could you tell) although close to the middle. I like to make the joke that Ps are always 5 minutes late, but don't think of that as being late ;)
N's tend to be big-picture, conceptual thinkers, whereas S's are detail-oriented and concrete.
J's are to-do list sorts of people, they enjoy finishing tasks, tend to "get a lot of stuff done", but can be stressed if there isn't a plan. P's prefer starting projects to finishing them, they tend to work off-the-cuff, probably appear to get less done, but are more capable of dealing with changing circumstances and priorities.
