During the month, Google sends out robots (spiders) to crawl the web and archive every website it finds. These archived websites will be presented in the next update of the Google index (database). The update process is initiated every 30 days or so, although on some occasions there have been more than 30 days between updates.
Google dance is an update to the ranking of the website according to their keywords, as ranking may increase or decrease according to the no. of visits....
when google updates there algorithm website keyword ranking will go up and down.this situation is called as google dance.
Google Dance refers to that stage when Google updates its search engine rankings. When the ranking goes increase and decrease in search engine result is called google dance.
Google dance is nothing, when it updates it serp then it says Google Dance.
Google dance is the fluctuation in position of keyword in SERPs. It occurs when mostly Panda or Penguin has been updated.