The word Geodesic describes a line traced around a sphere. Buckminster Fuller invented what we know today as a Geodesic Dome. Most traditional geodesic domes start off with either an octahedron, or more commonly an icosahedron (both types of polyhedra).
Each triangle face is divided in one of two ways as shown below. The first is known as a class I geodesic, the second is a class II geodesic dome.
The newly created intersections are pushed out so that they are an equal distance from the center of the polyhedra.
The number of intersections or the number of times the face triangles are divided, is known as the dome's frequency. Counting the triangles along each edge will tell you the frequency.
The pictures below show the difference in appearance between a Class I and a Class II geodesic.
