The "tag cloud" (far left) displays frequency distribution.
More frequently used tags receive a larger font.
The "tag shadow" (big box with dots) attempts to capture that frequency distribution in
a more visual medium. Try and embrace the "cloud" metaphor and imagine shining
a light through the above "tag cloud." Effectively what I've done is shine that
light from a whole bunch of different dirrections and found the most interesting
shadows. I've then plotted the 2 most useful shadows against each other.