Their new indexing system. Results are supposed to be more relevant and returned faster. When google passes a chunk of their index through their algorithm. Rankings fluctuate during this time. Used to happen every month like clockwork, now it's usually always happening. Pseudonym for googles supplemental index. An index that's queried only when the results from the primary index were dire. This is where you don't want your pages to be.
Google Caffeine is the new algorithm which Google wants to use since this year for indexing pages and ranking results. Google dance is when Google see a lot of backlinks for a new domain and it takes some time that Google be sure about the actual number of backlinks for this website. I don't know about Google hell
Here are the links that might help your doubt Google Caffiene:"googleblog.blogspot.com/2010/06/our-new-search-index-caffeine.html", Google Dance:"sefati.net/2010/07/google-dance-explained/" and Google Hell:"mattcutts.com/blog/google-hell/".
It's just the silly names given to Google's SERP behavior. You can come up with your own Google name as well
Google Dance happens when search engines update the backlinks of all websites and the effect of this is sometimes a temporary lost of good number of backlinks and losing your website on the SERP rankings. Google Caffeine is the new algorithm of Google it's advantages are fast indexing of websites and more fast search queries. Google Hell- what the hell is this?