Form and shape are areas or masses which define objects in space. Form and shape imply space; indeed they cannot exist without space.
There are various ways to categorize form and shape. Form and shape can be thought of as either two dimensional or three dimensional. Two dimensional form has width and height. It can also create the illusion of three dimension objects. Three dimensional shape has depth as well as width and height Form and shape can also be described as either organic or geometric. Organic forms such as these snow-covered boulders typically are irregular in outline, and often asymmetrical. Organic forms are most often thought of as naturally occurring.
Geometric forms are those which correspond to named regular shapes, such as squares, rectangles, circles, cubes, spheres, cones, and other regular forms. Architecture, such as this example by Frank Lloyd Wright, is usually composed of geometric forms. These forms are most often thought of as constructed or made. If you are interested in the visual possibilities of geometric forms, take a look at an index to images of mathematical origami, you might wish to look at this Web site, or at least at these mathematically generated forms.
