How to read /pos coordinates?

[Ponge]

Hello.

When you type a /pos command, you get 6 numbers; orientation is not important now, so let's see the other 3:
I know the second is the height from plane (pretty obvius: negative - down from plane; positive - above plane);
My question is: how do I read the other two? Which axis is the first one and what does the positive/nagative prefix mean (which direction on navmap), and same question for the last coordinate.

---