What is a cloud?
A "cloud," sometimes refered to as a "weighted list," is a grouping of labels where the size of the text is representative of the frequency of use of the items in the list. Also see: Wikipedia's definition of tag cloud.

"Tags" are arbitrary keywords associated with a given post. There can be zero, one, or more tags on a post. The larger the text, the more times that tag has been used to label a post. If someone creates a post with a tag of "Hot Dog," then we instantly have a new tag called "hot_dog."

The following is our current tag cloud: