Every objects that was sketched in AutoCAD's GUI based on a simple X,Y coordinate. In AutoCAD, this is called World Coordinate System (WCS). This is for simple 2d graphics, for 3Ds, there will be a new axis that is Z axis.
Pic 1.1 simple x,y coordinate on AutoCAD
AutoCAD use a point in a coordinate to define object;s position. This point defined relative to the origin point (0,0). All point must be defined relative to this center point. For example if you want to create a horizontal line from point 0,0 (it match x positive axis)
On above pic, a 9,6 coordinate, means the point is 9 in X axis and 6 units in Y axis . So when you work with AutoCAD, u have to define x point first, then the Y point.
For example (-10,-4) point, means this point is 10 point on the left of 0,0 (or x negative) and 4 point below Y axis
The second pic define how a line created between (-10,-4) and (9,6).
Pic 1.2 a line created from 10,4 to +9,+6
