The path definition contains absolute path elements (uppercase letters) and relative paths (lowercase letters).
In the next examples you can see both representations, in the "Code" areas.
Relative representation means that the element treats the previous point as the origin.
Absolute path element means that the point is independent of the previous one and is relative to the origin.
If you move the red dot in the first example, you can see that in the absolute representation only the coordinates of the red point change.
In the relative representation the coordinates of the blue dot also change, since the red point is it's origin and it moves.
If you overlap the red and the blue dot, you will notice that the relative one has the X and Y coordinates equal to 0.
Also, if you move the blue dot, the relative representation of the green one will change.
In the second example I reversed the roles. If you move the red dot you will notice that all the other points keep their positions relative to the previous one.
In this case, only the red dot coordinates change in the code of the relative representation.
Absolute and relative representations can alternate in the path definition.