Start with one fixed reference.
On a 2D grid, a point’s position is measured from the origin, (0, 0). X runs horizontally; Y runs vertically. In this demo the starting point A is (2, 3). The same pair of numbers can describe a destination or a movement, depending on the mode you choose.
Compare the two meanings.
Position (6, 4) places B at X = 6, Y = 4. Movement (6, 4) adds 6 and 4 to A, placing B at (8, 7). Neither calculation changes the starting point.
The interactive grid below keeps the axes fixed. It is an educational maths demo, not an AutoCAD simulator. All values are unitless.
Try the concept.
Connect the idea to CAD.
In AutoCAD, absolute Cartesian coordinates refer to the origin of the current user coordinate system (UCS); relative coordinates refer to the last point. The @ prefix marks relative input. With dynamic input at the cursor, # marks absolute input. Command-line entry and cursor input have different conventions; confirm which input method you are using.
The current UCS is the coordinate frame, not simply the direction you are looking. This 2D demo does not check a real drawing’s Z values.
To get from A (2, 3) to B (6, 4), the movement is (4, 1). If your demo shows B at (8, 7), you entered the destination as a movement. Change the mode or adjust the values, then check again.
Check the source
Command behaviour checked against the official references below. Interface details can vary by version and configuration.