[coolguy27]

Google also crawls and updates its index every day, so different or more index data usually isn’t an update either. The term “everflux” is often used to describe the constant state of low-level changes as we crawl the web and rankings consequently change to a minor degree. That’s normal, and that’s not an update...

from Source

When new indexing data is pushed out to data centers. From the summer of 2000 to the summer of 2003, index updates tended to happen about once a month. The resulting changes were called the Google Dance. The Google Dance occurred over the course of 6-8 days because each data center in turn had to be taken out of rotation and loaded with an entirely new web index, and that took time. In the summer of 2003 (the Google Dance called “Update Fritz”), Google switched to an index that was incrementally updated every day (or faster). Instead of a monolithic monthly event, the Google would refresh some of its index pretty much every day, which generated much smaller day-to-day changes that some people called everflux.

Over the years, Google’s indexing has been streamlined, to the point where most regular people don’t even notice the index updating. As a result, the terms “everflux,” “Google Dance,” and “index update” are hardly ever used anymore (or they’re used incorrectly ). Instead, most SEOs talk about algorithm updates or data updates/refreshes....

from Mattcutts Blog