This image describes Pathfinder's coordinate system, similar to what you'd find if you overlaid a cartesian plane on the game field, where the origin is where your robot starts.
On the graph above are plotted the waypoints:
[0, 0 @ 25 deg], [4.5, 2 @ 0 deg], [7.5, 3 @ 0 deg], [9, 1 @ 0 deg]
The heading is dependent on where your Gyroscope is zero'd to, which is usually where you set your robot up.
If you want to think of it another way, you could say that the X and Y axis are both parallel to the plane of the field carpet.