Absolute coordinates refers to a Cartesian System that uses x-axis, y-axis, and sometimes a z-axis to establish a point some distance from a common origin. For example, the picture's origin point is '0,0' and the absolute coordinate from that point is '8,7' making it 8 along the x-axis and 7 along the y-axis.
For example, in a CAD program you could draw a line using absolute coordinates. To do this start by entering the (x,y) value of your origin point. To start a line at one to the right, and four up, as shown in the picture, type 1,4. The line could then be drawn four to the right using the absolute coordinate of 5,4.