This double faced stone is used for sharpening ZWILLING J.A. HENCKELS stainless steel and carbon knives.
The light side (#1000) is for basic sharpening. Professionals usually start their sharpening with this side and amateurs often finish with it. With this side, you can achieve a satisfactory sharpness on the edge of your knives.
The darker, coarse side (#250) is used for repairing nicks in the edge of the knife and restoring the basic shape of the edge. Amateur users who don't sharpen that often are recommended to begin with a few strokes on this side for restoring the basic shape of the edge. Further details on how to use the stone are below.