Two-Step Stamping is when you use two or more coordinating stamps to create a complete image. A number of Stampin' Up! stamp sets feature Two-Step Stamping.
There are two types of Two-Step Stamping stamps. One is where you have two or more stamps with portions of a complete image. For example a flower head, stem and leaf. You can then stamp one or more to create a complete image in different colours.
The second type of two-step stamping is where you have a solid image and a matching outline or detail image. For this type you would stamp the solid image of, say, a flower in a subtle colour then stamp the outline or detail of that same flower over the top in a darker complimentary colour. This creates an image with colour variations and depth.
With Two-Step Stamping stamp sets you can choose to use the images on their own or combine them to create new and wonderful designs.