A typical cell hierarchy seen in XML viewer
A skin is basically a tree of graphical elements (cells) that compose a 2D User Interface. It is composed of a root cell (<SKIN> element), and children cells, that may also contain children cells.
Some elements cannot be seen by the user (layout only elements). Some are just passive elements that show some information to the user, and some allow the user to interact with them with the mouse or keyboard. Next chapter explains the main element families that can be used in Blue Cat's Skinning Language.