A zeitgeist is a visual representation of search trends. Basically, a zeitgeist tells you what people are looking for. The most-well known zeitgeist is Google's.
WP-Zeitgeist provides a way to display search engine query information in a fun and meaningful way.
WP-Zeitgeist is intended to be displayed as a cloud. Inside the cloud are links, the link text (what you see) is the actual unedited search engine query that brought a visitor to your site. The link portion (the click-through link) provides the actual page that was hit as a result of the query. The bigger the text, the more traffic your site has received from that query.