Take a look at the dropdown menu option when adding a new artwork in My Art.
Category describes the artwork as 2D (or two-dimensional - ex. painting on canvas, work on paper, etc) or 3D (or three-dimensional - ex. sculpture). We also specify if the work is part of an edition.
For example, if you have an Andy Warhol lithograph that is part of an edition that is numbered 11/30, then you would select 2D Edition from the drop down menu.