Alignment is by a vertex or a feature edge . Arrows indicate the directions of the X and Y axes.
Rotate coordinate system
or,
Right-click, and select Flip Axis.
Move coordinate system
If you click geometry that is not a vertex, right-click, choose Select Other, and then cycle through available geometry. Click the green dot to select.
The highlighted axis determines how the coordinates align (the highlighted axis aligns with the selected geometry). The sketch grid reorients to align with the coordinate system. You cannot align the axes to perpendicular geometry.